Anti-reflection film and display device using the same

ABSTRACT

An anti-reflection film comprises a high refractive index layer having a refractive index of 1.65-2.40, and a low refractive index layer having a refractive index of 1.20-1.55. Another anti-reflection film comprises only a low refractive index layer having a refractive index of 1.20-1.55. In the invention, the first improvement resides in a high refractive index layer composed of inorganic fine particles having a mean particle size of 1-200 nm in an amount of 5-65 vol. % and a crosslinked anionic polymer in an amount of 35 to 95 vol. %. The second improvement resides in a low refractive index layer composed of inorganic fine particles having a mean particle size of 0.5-200 nm in an amount of 50-95 wt. % and a polymer in an amount of 5-50 wt. %, and two or more of those particles are piled up to form micro voidsby the adjacent particles.

FIELD OF THE INVENTION

The present invention relates to an anti-reflection film comprising ahigh refractive index layer and a low refractive index layer, ananti-reflection film comprising a low refractive index layer, and adisplay device using the anti-reflection film.

PRIOR ART

Anti-reflection films are used in various display devices such as aliquid crystal display device (LCD), a plasma display panel (PDP), anelectroluminescence display (ELD), and a cathode-ray tube (CRT).Further, they are generally provided on lenses of glasses or cameras.

As the anti-reflection film, a multi-layered film comprising pluraltransparent metal oxide layers superposed one on another has been widelyemployed. The plural transparent metal oxide layers reduce reflectionsof light in a wide wavelength region, and are formed by chemical vapordeposition (CVD) process or physical vapor deposition (PVD) process(especially, vacuum deposition process). Although the transparent metaloxide layers give an anti-reflection film having excellent opticalcharacteristics, the deposition process has insufficient productivityfor mass-production.

In place of the deposition process, it is proposed to employ a coatingliquid containing inorganic fine particles to prepare an anti-reflectionfilm.

Japanese Patent Publication No. 60-59250 describes an anti-reflectionfilm comprising fine holes and inorganic fine particles. The film isformed by using a coating liquid, and the formed film is subjected toactive gas treatment. By the treatment, the gas escapes from the film toform the fine holes.

Japanese Patent Provisional Publication No. 59-50401 describes ananti-reflection film comprising a support, a high refractive index layerand a low refractive index layer superposed in order. This publicationalso discloses an anti-reflection film further comprising a middlerefractive index layer provided between the support and the highrefractive index layer. In each film, the low refractive index layer isformed by using a coating liquid containing a polymer or inorganic fineparticles.

Japanese Patent Provisional Publication No. H2-245702 discloses ananti-reflection film comprising two or more kinds of micro particles(for example, SiO₂ and MgF₂). The mixing ratio of the particles variesin the thickness direction so that the refractive index would graduallyvary in the thickness direction. The film having that structure hasoptical characteristics similar to those of the film in No. 59-50401,which comprises both high and low refractive index layers. In the filmof Publication No. H2-245702, the micro particles are combined via SiO₂formed by thermal decomposition of ethyl silicate. In the thermaldecomposition, the ethyl part of ethyl silicate is burnt to evolvecarbon dioxide and water vapor. The produced carbon dioxide and watervapor escape from the film to form voids by the adjacent micro particles(as shown in FIG. 1 of the publication).

Japanese Patent Provisional Publication No. H5-13021 discloses ananti-reflection film in which the voids described in Publication No.2(1990)-245702 are filled with a binder.

Japanese Patent Provisional Publication No. H7-48527 discloses ananti-reflection film comprising a binder and inorganic fine particles ofporous silica.

Japanese Patent Provisional Publications No. H8-110401 and No. H8-179123disclose an anti-reflection film which comprises a high refractive indexfilm (having a refractive index of 1.80 or more) containing inorganicfine particles of high refractive index dispersed in a plastic material.

SUMMARY OF THE INVENTION

The present inventors made studies on incorporation of inorganic fineparticles into a high refractive index layer and a low refractive indexlayer of anti-reflection film. For forming the layers, it isadvantageous to employ a coating liquid containing inorganic fineparticles, because the process has enough productivity formass-production. However, the inventors noted the problems in formingthe layers of high and low refractive indexes.

In forming a high refractive index layer, it is difficult to finelydisperse the inorganic particles and further to form the layer having awell dispersed phase.

For preparing a high refractive index layer as a transparent film, theinorganic particles need to be dispersed finely and uniformly. It isgenerally known that surface active agents and (cationic or anionic)polymers are used for dispersing the particles. Those agents can be usedonly when the layer is formed. After forming the layer, they show nofunction, and further often impair physical strength (abrasionresistance) and chemical strength (chemical resistance) of the highrefractive index layer.

It is also difficult to prepare a low refractive index layer having botha proper refractive index and enough physical strength.

The study of the inventors revealed that the refractive index can bedecreased by micro voids in the layer. By piling up two or moreinorganic fine particles in the layer, the micro voids can be formedbetween the particles. However, a low refractive index layer containingthe voids generally has insufficient strength. Since the low refractiveindex layer is often placed on the screen of image display device or theouter surface of lens, the layer needs to have enough strength. If thevoids are filled with a binder the layer has sufficient strength.However, according to the study of the inventors, such voids can notsatisfyingly lower the refractive index of the layer.

An object of the invention is to provide an anti-reflection filmsuitable for mass-production.

Another object of the invention is to provide an anti-reflection filmcomprising a transparent high refractive index layer having an increasedhigh refractive index.

Further, it is also an object of the invention to provide ananti-reflection film comprising a low refractive index layer having andecreased low refractive index.

Furthermore, it is an object of the invention to provide ananti-reflection film comprising a high or low refractive index layerhaving excellent strength.

In addition, an object of the invention is to provide a display devicein which the reflection of light is lowered by proper means.

The objects of the invention are achieved by the following improvements(1) to (4) of high refractive index layer, the following improvements(10) to (13) of low refractive index layer, the following improvements(5) to (8) of both layers, and the following display devices (9) and(14) equipped with improved anti-reflection films.

(1) An anti-reflection film comprising a high refractive index layerhaving a refractive index of 1.65 to 2.40 and a low refractive indexlayer having a refractive index of 1.20 to 1.55, wherein the highrefractive index layer contains inorganic fine particles having a meanparticle size of 1 to 200 nm in an amount of 5 to 65 vol. % and acrosslinked polymer comprising phosphoric acid group or sulfonic acidgroup as an anionic group in an amount of 35 to 95 vol. %.

(2) The anti-reflection film of (1), wherein the polymer having theanionic group in the high refractive index layer further contains aminogroup or ammonium group.

(3) The anti-reflection film of (1), wherein the inorganic fineparticles in the high refractive index layer have an average refractiveindex of 1.80 to 2.80.

(4) The anti-reflection film of (1), wherein the high refractive indexlayer is formed by applying a coating liquid, and the polymer having theanionic group is formed by polymerization reaction during or after theapplication.

(5) The anti-reflection film of (1), wherein the low refractive indexlayer contains inorganic fine particles having a mean particle size of0.5 to 200 nm in an amount of 50 to 95 wt. % and a polymer in an amountof 5 to 50 wt. %, and two or more of said particles are piled up to formmicro voids between the adjacent particles.

(6) The anti-reflection film of (5), wherein the low refractive indexlayer has a void volume in the range of 3 to 50 vol. %.

(7) The anti-reflection film of (5), wherein the inorganic fineparticles in the low refractive index layer are coated with a shell ofpolymer.

(8) The anti-reflection film of (5), wherein the micro voids in the lowrefractive index layer are enclosed with the inorganic particles and thepolymer.

(9) A display device having an anti-reflection film provided on thedisplay screen, wherein

the anti-reflection film comprises a high refractive index layer havinga refractive index of 1.65 to 2.40 and a low refractive index layerhaving a refractive index of 1.20 to 1.55, and t

he high refractive index layer contains inorganic fine particles havinga mean particle size of 1 to 200 nm in an amount of 5 to 65 vol. % and acrosslinked polymer comprising phosphoric acid group or sulfonic acidgroup as an anionic group in an amount of 35 to 95 vol. %.

(10) An anti-reflection film comprising a low refractive index layerhaving a refractive index of 1.20 to 1.55, wherein

the low refractive index layer contains inorganic fine particles havinga mean particle size of 0.5 to 200 nm in an amount of 50 to 95 wt. % anda polymer in an amount of 5 to 50 wt. %, and two or more of saidparticles are piled up to form micro voids among the particles.

(11) The anti-reflection film of (10), wherein the void ratio in the lowrefractive index layer is in the range of 3 to 50 vol. %.

(12) The anti-reflection film of (10), wherein the inorganic fineparticles in the low refractive index layer are coated with shells madeof a polymer.

(13) The anti-reflection film of (10), wherein the micro voids in thelow refractive index layer are enclosed with the inorganic particles andthe polymer.

(14) A display device having an anti-reflection film provided on thedisplay screen, wherein

the anti-reflection film comprises a low refractive index layer having arefractive index of 1.20 to 1.55, and

the low refractive index layer contains inorganic fine particles havinga mean particle size of 0.5 to 200 nm in an amount of 50 to 95 wt. % anda polymer in an amount of 5 to 50 wt. %, and two or more of saidparticles are piled up to form micro voids among the particles.

According to the study of the inventors, the inorganic particles in thehigh refractive index layer can be finely dispersed and the layer can beformed with that fine dispersion maintained by incorporating thecrosslinked polymer comprising phosphoric acid group or sulfonic acidgroup as an anionic group in an amount of 35 to 95 vol. %. Beforeforming the high refractive index layer, monomers having the anionicgroup polymerizable to form the polymer having the anionic group serveas an excellent dispersant for the inorganic particles. After formingthe layer, the monomers having the anionic group are polymerized andcrosslinked to form the crosslinked polymer having the anionic group.The inorganic particles are firmly bound with the crosslinked polymerhaving the anionic group to give excellent strength to the layer.

The inventors also succeeded in binding the inorganic particles in thelow refractive index layer with a polymer without filling the microvoids with the polymer. Two or more of the particles are piled up toform the micro voids among the particles to give a very low refractiveindex. Further, since the particles are bound with the polymer,satisfying strength can be given. Furthermore, since the micro voids arenot filled with the polymer, they can sufficiently lower the refractiveindex of the layer.

The thus improved high or low refractive index layer can be easilyformed by applying a coating liquid, and hence is suitable formass-production. In an anti-reflection film comprising both high and lowrefractive index layers, the film strength can be improved by combiningthose improved layers. Further, in a display device, the reflection oflight on the display screen can be effectively lowered with the thusimproved anti-reflection film.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows schematic cross-sectional views of various examples of theanti-reflection film.

FIG. 2 is a schematic cross-sectional view of the high refractive indexlayer.

FIG. 3 is a schematic cross-sectional view of the low refractive indexlayer.

EMBODIMENTS OF THE INVENTION Layer Structure of Anti-reflection Film

By referring to FIG. 1, the layer structure of the anti-reflection filmis explained below.

FIG. 1 shows cross-sectional views of various examples of theanti-reflection film.

The embodiment shown in FIG. 1(a) comprises a transparent support (3), ahard coating layer (2), and a low refractive index layer (1) superposedin order.

If the anti-reflection film is provided on a surface of hard materialsuch as glass (e.g., on a display screen of CRT, or on a lens of glassesor camera), the hard coating layer (2) and the low refractive indexlayer (1) may be directly formed on the surface with using notransparent support (3).

The embodiment shown in FIG. 1(b) comprises a transparent support (3), ahard coating layer (2), a high refractive index layer (4) and a lowrefractive index layer (1) superposed in order.

Generally in a film comprising both high and low refractive index layerssuch as the film of FIG. 1(b), the high refractive index layer (4) andthe low refractive index layer (1) preferably satisfy the followingformulas (I) and (II), respectively, as described in Japanese PatentProvisional Publication No. 59-50401:

 m/4λ×0.7<n₁d₁<m/4λ×1.3  (I)

in which m represents a positive integer (generally 1, 2 or 3), n₁represents a refractive index of the high refractive index layer, d_(l)represents a thickness (nm) of the high refractive index layer; and

n/4λ×0.7<n₂d₂<n/4λ×1.3  (II)

in which n represents a positive odd number (generally 1), n₂ representsa refractive index of the low refractive index layer, and d₂ representsa thickness (nm) of the low refractive index layer.

The embodiment shown in FIG. 1(c) comprises a transparent support (3), ahard coating layer (2), a middle refractive index layer (5), a highrefractive index layer (4) and a low refractive index layer (1)superposed in order.

In a film comprising middle, high and low refractive index layers suchas the film of (c), the middle, high and low refractive index layerspreferably satisfy the following formulas (III) to (V), respectively, asdescribed in Japanese Patent Provisional Publication No. 59-50401:

h/4λ×0.7<n₃d₃<h/4λ×1.3  (III)

in which h represents a positive integer (generally 1, 2 or 3), n₃represents a refractive index of the middle refractive index layer, d₃represents a thickness (nm) of the middle refractive index layer;

j/4λ×0.7<n₄d₄<j/4λ×1.3  (IV)

in which j represents a positive integer (generally 1, 2 or 3), n₄represents a refractive index of the high refractive index layer, d₄represents a thickness (nm) of the high refractive index layer; and

k/4λ×0.7<n₅d₅<k/4λ×1.3  (V)

in which k represents a positive odd number (generally 1), ns representsa refractive index of the low refractive index layer, and d₅ representsa thickness (nm) of the low refractive index layer.

The high or low refractive index layer improved according to theinvention can be applied for the anti-reflection films of layeredstructures. Even in combination with a conventional low refractive indexlayer, the high refractive index layer of the invention effectivelyimproves the anti-reflection film. Also, the low refractive index layerof the invention effectively improves the film even in combination witha conventional high refractive index layer. Further, even without thehigh refractive index layer, the low refractive index layer of theinvention can give an excellent anti-reflection film as shown in FIG.1(a). Of course, a combination of the high and low refractive indexlayers of the invention gives a remarkably improved film.

The conventional high and low refractive index layers are described inpublications of prior art, and hence the high refractive index layer andthe low refractive index layer improved according to the invention areexplained below in this order.

High Refractive Index Layer

FIG. 2 is a schematic cross-sectional view of a high refractive indexlayer. Above the high refractive index layer of FIG. 2, a low refractiveindex layer is placed. A display device or a lens is placed below thehigh refractive index layer.

The high refractive index layer (4) of FIG. 2 contains no void, and apolymer (42) is charged among inorganic fine particles (41). In the highrefractive index layer (4), the inorganic fine particles (41) having amean particle size of 1 to 200 nm are piled up (in FIG. 2, threeparticles are piled up). Among the inorganic fine particles (41), thecrosslinked polymer comprising phosphoric acid group or sulfonic acidgroup as an anionic group (43) is charged.

The high refractive index layer has a refractive index of 1.65 to 2.40,preferably 1.70 to 2.20. The refractive index can be measured by meansof a Abbe's refractometer, or estimated according to light reflection onthe surface of the layer.

The thickness of the high refractive index layer preferably is in therange of 5 nm to 100 μm, more preferably 10 nm to 10 μm, and furtherpreferably 30 nm to 1 μm.

The haze of the high refractive index layer is preferably in the rangeof not more than 5%, more preferably not more than 3%, and furtherpreferably not more than 1%.

The high refractive index layer improved according to the invention hasan excellent strength. The layer preferably has a mechanical strength ofnot lower than H, more preferably not lower than 2H, further preferablynot lower than 3H in terms of pencil grades under a load of 1 kgw.

Inorganic Fine Particles in High Refractive Index Layer

Inorganic fine particles in the high refractive index layer preferablyhave a refractive index of 1.80 to 2.80, more preferably 1.90 to 2.80.

The weight mean size of the inorganic fine particles in primaryparticles is preferably in the range of 1 to 150 nm, more preferably 1to 100 nm, further preferably 1 to 80 nm.

In the formed high refractive index layer, the inorganic fine particleshave a weight mean size of 1 to 200 nm, preferably 5 to 150 nm, morepreferably 10 to 100 nm, and further preferably 10 to 80 nm.

The particle size can be determined by light-scattering or electronmicrography.

The inorganic fine particles preferably have a specific surface area of10 to 400 m²/g, more preferably 20 to 200 m²/g, further preferably 30 to150 m²/g.

Preferably, the inorganic fine particles are made of metal oxides orsulfides. Examples of the metal oxides or sulfides include titaniumdioxide (e.g., of rutile, mixed crystal of rutile/anatase, anatase,amorphous structure), tin oxide, indium oxide, zinc oxide, zirconiumoxide, and zinc sulfide. Preferred are titanium oxide, tin oxide, andindium oxide. The inorganic fine particles may contain other elements,as well as those oxides or sulfides of main component. The term of “maincomponent” here means a component contained in the largest content (wt.%). Examples of the other elements include Ti, Zr, Sn, Sb, Cu, Fe, Mn,Pb, Cd, As, Cr, Hg, Zn, Al, Mg, Si, P, and S.

The inorganic fine particles may be subjected to surface treatment,which can be performed using inorganic compounds or organic compounds.Examples of the inorganic compounds include alumina, silica, zirconiumoxide, and iron oxide. Alumina and silica are preferred. Examples of theorganic compounds include polyol, alkanolamine, stearic acid, silanecoupling agents, and titanate coupling agents. Silane coupling agentsare particularly preferred. These may be used in combination.

The shape of the inorganic fine particles preferably is grain shape,globular shape, cubic shape, droplet shape, or irregular shape.

Two or more kinds of inorganic fine particles may be contained in thehigh refractive index layer.

The high refractive index layer contains the inorganic fine particles inan amount of 5 to 65 vol. %, preferably 10 to 60 vol. %, more preferably20 to 55 vol. %.

In forming the high refractive index layer, the particles areincorporated in the form of dispersion. The medium of the dispersion ispreferably a liquid having a boiling point of 60 to 170° C. Example ofthe medium include water, alcohols (e.g., methanol, ethanol,isopropanol, butanol, benzyl alcohol), ketones (e.g., acetone, methylethyl ketone, methyl isobutyl ketone, cyclohexanone), esters (e.g.,methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methylformate, ethyl formate, propyl formate, butyl formate), aliphatichydrocarbons (e.g., hexane, cyclohexane), halogenated hydrocarbons(e.g., methylene chloride, chloroform, carbon tetrachloride), aromatichydrocarbons (e.g., benzene, toluene, xylene), amides (e.g.,dimethylformamide, dimethylacetamide, n-methylpyrrolidone), ethers(e.g., diethyl ether, dioxane, tetrahydrofuran), and ether alcohol(e.g., 1-methoxy-2-propanol). Preferred ones are toluene, xylene, methylethyl ketone, methyl isobutyl ketone, cyclohexanone, and butanol.

The inorganic fine particles can be dispersed in the medium by means ofa dispersing machine such as a sand grinder mill (e.g., a beads-millequipped with pins), a high speed impeller mill, a pebble mill, a rollermill, an attriter, and a colloid mill. A sand grinder mill and a highspeed impeller mill are particularly preferred. Prior to dispersing,pre-dispersing may be performed. Examples of the dispersing machine forpre-dispersing include a ball mill, a three-roller mill, a kneader, andan extruder.

Binder in High Refractive Index Layer

The high refractive index layer of the invention is characterized bycontaining a crosslinked polymer comprising phosphoric acid group orsulfonic acid group as an anionic group.

The polymer has a crosslinked main chain having anionic groups, whichmaintain the dispersion of the inorganic fine particles. The crosslinkedstructure gives film-formability so as to enhance the high refractiveindex layer.

Examples of the main chain include those of polyolefin (saturatedhydrocarbon), polyether, polyurea, polyurethane, polyester, polyamine,polyamide, and melamine resin. The main chains of polyolefin, polyether,and polyurea are preferred. More preferred ones are those of polyolefinand polyether, and the main chain of polyolefin is further preferred.

The main chain of polyolefin consists of saturated hydrocarbons, and is,for example, prepared by addition polymerization of unsaturatedpolymerizable groups. The main chain of polyether consists of repeatingunits combined with ether bonding (—O—), and is, for example, preparedby ring-opening polymerization of epoxy groups. The main chain ofpolyurea consists of repeating units combined with urea bonding(—NH—CO—NH—), and is, for example, prepared by condensationpolymerization between isocyanate group and amino group. The main chainof polyurethane consists of repeating units combined with urethanebonding (—NH—CO—O—), and is, for example, prepared by condensationpolymerization between isocyanate group and hydroxyl group (includingN-methylol group). The main chain of polyester consists of repeatingunits combined with ester bonding (—CO—O—), and is, for example,prepared by condensation polymerization between carboxyl group(including acid halide group) and hydroxyl group (including N-methylolgroup). The main chain of polyamine consists of repeating units combinedwith imino bonding (—NH—), and is, for example, prepared by ring-openingpolymerization of ethylene imine group. The main chain of polyamideconsists of repeating units combined with amido bonding (—NH—CO—), andis, for example, prepared by reaction between isocyanate group andcarboxyl group (including acid halide group). Melamine resin has acrosslinked main chain, which can be prepared by condensationpolymerization between triazine group (e.g., melamine) and aldehyde(e.g., formaldehyde).

The anionic group is combined with the main chain of the polymerdirectly or via a linking group. Preferably, the anionic group is at aside chain combined with the main chain via a linking group.

The anionic group is sulfonic acid group (sulfo group) or phosphoricacid group (phosphono group). The anionic group may be in the form ofsalts. In that case, cations forming the salt with the anionic group arepreferably ions of alkali metals. The anionic group may be dissociatedto release a proton. Examples of the linking group connecting betweenthe anionic group and the main chain include —CO—, —O—, alkylene group,arylene group, and a divalent group derived from combination of these.

In the crosslinked structure, two or more main chains are chemicallycombined (preferably with covalent bonds). The crosslinked structurepreferably comprises three or more main chains combined with covalentbonds. Preferably, the crosslinked structure contains —CO—, —O—, —S—,nitrogen atom, phosphorus atom, aliphatic residues, aromatic residues,and a divalent group derived from combination of these.

As the polymer, a copolymer comprising a repeating unit having ananionic group and one having a crosslinked structure is preferably used.The repeating unit having an anionic group is preferably contained in anamount of 2 to 96 wt. %, more preferably 4 to 94 wt. %, furtherpreferably 6 to 92 wt. %. That repeating unit may have two or more kindsof anionic groups.

The repeating unit having a crosslinked structure is preferablycontained in an amount of 4 to 98 wt. %, more preferably 6 to 96 wt. %,further preferably 8 to 94 wt. %.

The polymer may comprise a repeating unit having both an anionic groupand a crosslinked structure.

In the polymer, other repeating units (having neither anionic group norcrosslinked structure) may be contained. Preferred other repeating unitsinclude a repeating unit having an amino group or a quaternary ammoniumgroup, or one having a benzene ring. Similarly to anionic groups, theamino group and the quaternary ammonium group maintain the dispersion ofthe inorganic fine particles. The benzene ring increases the refractiveindex of the high refractive index layer. Those effects of amino group,quaternary ammonium group and benzene ring can be obtained even if theyare incorporated in the repeating unit having an anionic group or acrosslinked structure.

In the repeating unit having an amino group or a quaternary ammoniumgroup, the amino or quaternary ammonium group is combined with the mainchain of the polymer directly or via a linking group. Preferably, thegroup is present as a side chain combined with the main chain via alinking group. Preferred amino or quaternary ammonium group is secondaryamino group, tertiary amino group, or quaternary ammonium group.Tertiary amino group and quaternary ammonium group are more preferred.The nitrogen atom of secondary amino group, tertiary amino group, orquaternary ammonium group is preferably connected to an alkyl group,more preferably an alkyl group having 1 to 12 carbon atoms, furtherpreferably an alkyl group having 1 to 6 carbon atoms. The counter ion ofthe quaternary ammonium group preferably is a halide ion. Examples ofthe linking groups connecting the amino or quaternary ammonium group andthe main chain include —CO—, —NH—, —O—, alkylene group, arylene group,and a divalent group derived from combination of these.

If the polymer contains the repeating unit having an amino or quaternaryammonium group, the content of that unit is preferably in the range of0.06 to 32 wt. %, more preferably 0.08 to 30 wt. %, further preferably0.1 to 28 wt. %.

In the repeating unit having a benzene ring, the ring is combined withthe main chain of the polymer directly or via a linking group.Preferably, the ring is at a side chain combined with the main chain viaa linking group. The benzene ring may have a substituent (e.g., alkylgroups, hydroxyl group, halogen atoms). Examples of the linking groupconnecting between the benzene ring and the main chain include —CO—,—O—, alkylene group, arylene group, and a divalent group derived fromcombination of these.

If the polymer contains the repeating unit having a benzene ring, thecontent of that unit is preferably in the range of 2 to 98 wt. %, morepreferably 4 to 96 wt. %, further preferably 6 to 94 wt. %.

In a polymer having a particularly preferred main chain of polyofefin,examples of a repeating unit having an anionic group (VI), a repeatingunit having a crosslinked structure (VII), a repeating unit having bothan anionic group and a crosslinked structure (VIII), a repeating unithaving an amino or quaternary ammonium group (IX), and a repeating unithaving a benzene ring (X) are shown below. The shown examples of therepeating unit (VIII) includes the unit (VIIIb) having a carboxylicgroup as an anionic group. If the unit (VIIIb) is employed for theinvention, it is necessary to combine the unit (VIIIb) with the unit(VI) having sulfonic acid group or phosphoric acid group as an anionicgroup, to form a copolymer.

In the formula, R¹ is hydrogen atom or methyl group, L¹ is a divalentlinking group, and An is sulfonic acid group or phosphoric acid group.

In the formula (VI), L¹ is preferably a divalent linking group selectedfrom the group consisting of —CO—, —O—, alkylene group, arylene group,and a divalent group derived from combination of these. The alkylenegroup preferably has 1 to 20, more preferably 1 to 15, furtherpreferably 1 to 10 carbon atoms, and may form a ring. The arylene grouppreferably has 6 to 20, more preferably 6 to 15, further preferably 6 to10 carbon atoms. The alkylene and arylene group may have a substituent(e.g., alkyl groups, hydroxyl group, halogen atoms).

Concrete examples of L¹ are shown below. In each following formula, theleft and right ends are connected to the main chain and An,respectively. AL and AR represent an alkylene group and an arylenegroup, respectively.

L¹¹: —CO—O—AL—(O—CO—AL)_(m1)— (m1 is a positive integer)

L¹²: —CO—O—(AL—O)_(m2)—AR—AL—AR—(O—AL)_(m3)—

(each of m2 and m3 is a positive integer)

L¹³: —CO—O—AL—

L¹⁴: —CO—O—AL—O—CO—

L¹⁵: —CO—O—AL—O—CO—AR—

L¹⁶: —CO—O—AL—O—CO—AL—

The sulfonic acid group or phosphoric acid group of An in (VI) isdescribed before.

The repeating unit of (VI) can be prepared by condensationpolymerization of corresponding ethylenic unsaturated monomers. Examplesof the ethylenic unsaturated monomers include: bis(polyoxyethylenepolycyclic phenylether) methacrylate sulfuric ester salt, 2-sulfoethylmethacrylate, phthalic monohydroxyethylacrylate, acrylic acid dimer,2-acrylolyoxyethylhydrogen phthalate, 2-acrylolyoxypropylhydrogenphthalate, 2-acrylolyoxypropylhexahydrohydrogen phthalate,2-acrylolyoxypropyltetrahydrohydrogen phthalate,β-acrylolyoxyethylhydrogen succinate, β-methacrylolyoxyethylhydrogenfumarate, β-methacrylolyoxyethylhydrogen succinate,mono(2-acryloyloxyethyl)acid phosphate, andmono(2-methacryloyloxyethyl)acid phosphate. Commercially availableethylenic unsaturated monomers having these anionic groups are alsoemployable.

In the formula, R² is hydrogen atom or methyl group, n is an integer ofnot less than 2, and L² is a hydrocarbon residue of n-valent.

In the formula (VII), n is preferably an integer of 2 to 20, morepreferably 2 to 10, further preferably 3 to 6. The residue of L²preferably is an aliphatic residue (more preferably a saturatedaliphatic residue). The aliphatic residue may contain an ether bond(—O—), and may have a branched chain. Preferably, the residue of L²comprises 1 to 20, more preferably 2 to 15, further preferably 3 to 10carbon atoms.

The repeating unit of (VII) can be prepared by condensationpolymerization of corresponding ethylenic unsaturated monomers, whichare esters between (meth)acrylic acid and polyhydric alcohols or phenols(preferably, polyhydric alcohols) corresponding to L²-(—OH)_(n).Examples of the ethylenic unsaturated monomers include: neopentyl glycolacrylate, 1,6-hexanediol acrylate, alkylene glycols such as propyleneglycol diacrylate, triethylene glycol diacrylate, dipropylene glycoldiacrylate, polyethylene glycol diacrylate, polypropylene glycoldiacrylate, pentaerythritol diacrylate,bis{4-(acryloxy•diethoxy)phenyl}propane,bis{4-(acryloxy•polypropoxy)phenyl}propane, trimethylolpropanetri(meth)acrylate, trimethylolethane tri(meth)acrylate,1,2,4-cyclohexane tetramethacrylate, pentaglycelol triacrylate,pentaerythritol tetra(meth)acrylate, pentaerythritol tri(meth)acrylate,(di)pentaerythritol triacrylate, (di)pentaerythritol pentaacrylate,(di)pentaerythritol tetra(meth)acrylate, (di)pentaerythritolhexa(meth)acrylate, tripentaerythritol triacrylate, andtripentaerythritol hexatriacrylate. Commercially available estersbetween (meth)acrylic acid and polyhydric alcohols are also employable.

In the formulas, each of R³¹, R³², R³³ and R³⁴ is independently hydrogenatom or methyl group, and each of L³¹ and L³² is independently adivalent linking group.

In the formulas (VIII-a) and (VIII-b), each of L³¹ and L³² is preferablya divalent linking group selected from the group consisting of —CO—,—O—, alkylene group, arylene group, and a divalent group derived fromcombination of these. The alkylene group preferably has 1 to 20, morepreferably 1 to 15, further preferably 1 to 10 carbon atoms, and mayform a ring. The arylene group preferably has 6 to 20, more preferably 6to 15, further preferably 6 to 10 carbon atoms. The alkylene and arylenegroup may have a substituent (e.g., alkyl groups, hydroxyl group,halogen atoms).

Concrete examples of L³¹ and L³² are the same as those described for L¹(i.e., L¹¹ to L¹⁶).

The repeating units of (VIII-a) and (VIII-b) can be prepared bycondensation polymerization of corresponding ethylenic unsaturatedmonomers. Examples of the ethylenic unsaturated monomers for (VIII-a)include a reaction product between phosphoric acid anhydride and6-hexanolide addition polymer of 2-hydroxyethylmethacrylate,bis(methacryloxyethyl)phosphate, 2-acryloyloxyethyl acid phosphate, and2-methacryloyloxyethyl acid phosphate. Examples of the ethylenicunsaturated monomers for (VIII-b) include β-acrylolyoxyethylhydrogenfumarate, and β-acrylolyoxyethyl-hydrogen maleate. Commerciallyavailable ethylenic unsaturated monomers are also employable.

In the formulas, each of R⁴¹, R⁴² and R⁴³ independently is hydrogen atomor methyl group, each of L⁴, L^(4a) and L^(4b) independently ia adivalent linking group, and Am is an amino group or a quaternaryammonium group.

In the formulas (IX-a) and (IX-b), each of L⁴, L^(4a) and L⁴b preferablyis a divalent linking group selected from the group consisting of —CO—,—NH—, —O—, alkylene group, arylene group, and a divalent group derivedfrom combination of these. The alkylene group preferably has 1 to 20,more preferably 1 to 15, further preferably 1 to 10 carbon atoms, andmay form a ring. The arylene group preferably has 6 to 20, morepreferably 6 to 15, further preferably 6 to 10 carbon atoms. Thealkylene and arylene group may have a substituent (e.g., alkyl group,hydroxyl group, halogen atom).

Concrete examples of L⁴, L^(4a) and L^(4b) are shown below. In eachfollowing formula, the left and right ends are connected to the mainchain and Am, respectively. AL represents an alkylene group.

L⁴¹: —CO—O—AL—

L⁴²: —CO—O—NH—AL—

L⁴³: —AL—

The amino group or quaternary ammonium group of Am in (IX-a) and (IX-b)is described before.

The repeating units of (IX-a) and (IX-b) can be prepared by condensationpolymerization of corresponding ethylenic unsaturated monomers. Examplesof the ethylenic unsaturated monomers for (IX-a) includedimethylaminoethyl acrylate, dimethylaminopropyl acrylamide, methacrylicacid hydroxypropyltrimethylammonium chloride, dimethylaminopropylmethacrylamide, and methacrylamidepropyl trimethylammonium chloride.Examples of the ethylenic unsaturated monomers for (IX-b) includediacryldimethylammonium chloride. Commercially available ethylenicunsaturated monomers having amino group or quaternary ammonium group arealso employable.

In the formula, R⁵¹ is hydrogen atom or methyl group; R⁵² is hydrogenatom, carboxyl group, an alkyl group having 1 to 6 carbon atoms, or ahalogen atom; and L⁵ is a monovalent bond or a divalent linking group.

If R⁵² is carboxyl group in the formula (X), R⁵² is preferably connectedto the ortho position of the benzene ring.

In the formula (X), L⁵ is preferably a divalent group derived fromcombination of —CO—, —O— and alkylene group. The alkylene grouppreferably has 1 to 20, more preferably 1 to 15, further preferably 1 to10 carbon atoms, and may form a ring. The alkylene group may have asubstituent (e.g., alkyl groups, hydroxyl group, halogen atoms).

Concrete examples of L⁵ are shown below. In each following formula, theleft and right ends are connected to the main chain and the benzenering, respectively. AL represents an alkylene group.

L⁵⁰: monovalent bond

L⁵¹: —CO—O—(AL—O)_(m4)— (m4 is a positive integer)

L⁵²: —CO—O—AL—

The repeating unit of (X) can be prepared by condensation polymerizationof corresponding ethylenic unsaturated monomers. Examples of theethylenic unsaturated monomers include phenoxyethyl acrylate,phenoxypolyethylene glycol acrylate, 2-hydroxy-3-phenoxypropyl acrylate,2-acryloyloxyethyl-2-hydroxyethylphthalic acid, and2-acryloyloxyethylphthalic acid. Commercially available ethylenicunsaturated monomers having benzene ring are also employable.

If the polymer has a main chain of polyether derived from epoxy group,repeating units in which oxygen atom (—O—) is connected to the left endof ethylene group (—CH₂—) of the above-described repeating units areusable.

The crosslinked polymer comprising phosphoric acid group or sulfonicacid group as an anionic group is preferably formed in the followingmanner. During or after applying the coating liquid (the aforementioneddispersion of inorganic fine particles) for the high refractive indexlayer, the monomers are added to the liquid and polymerized to form thepolymer. The monomers having phosphoric acid group or sulfonic acidgroup as an anionic group serve as a dispersant for the inorganicparticles in the coating liquid, and are preferably incorporated in anamount of 1 to 50 wt. %, more preferably 5 to 40 wt. %, furtherpreferably 10 to 30 wt. %. On the other hand, the monomers having aminogroup or quaternary ammonium group serve as a dispersing aid in thecoating liquid, and are preferably used in an amount of 3 to 33 wt. %based on those having an anionic group. If the polymer is formed duringor after applying the coating liquid, those monomers effectively workbefore the application.

The reaction for forming the polymer may be photopolymerization orthermal polymerization. Photopolymerization is preferred.

For polymerization reaction, polymerization initiators are preferablyused. Examples of polymerization initiators include acetophenones,benzoins, benzophenones, phosphine oxides, ketals, anthraquinones, azocompounds, peroxides, 2,3-dialkyldione compounds, disulfido compounds,fluoroamine compounds, and aromatic sulfoniums. Examples ofacetophenones include 2,2-doethoxyacetophenone, p-dimethylacetophenone,1-hydroxydimethylphenyl ketone, 1-hydroxycyclohexylphenyl ketone,2-methyl-4-methylthio-2-morpholinopropiophenone, and2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone. Examples ofbenzoins include benzoin methyl ether, benzoin ethyl ether, and benzoinisopropyl ether. Examples of benzophenones include benzophenone,2,4-dichlorobenzophenone, 4,4-dichlorobenzophenone, andp-chlorobenzophenone. Examples of phosphine oxides include2,4,6-trimethylbenzoyldiphenylphosphine oxide. Commercially availablepolymerization initiators can be also used. In addition to theinitiators, polymerization promoters may be used. The amount ofpolymerization initiators and promoters are in the range of 0.2 to 10wt. % based on the total amount of the monomers.

If the polymer is formed by photopolymerization, light sources such aslow pressure mercury lamp, high pressure mercury lamp, ultra-highpressure mercury lamp, chemical lamp and metal halide lamp are used. Ahigh pressure mercury lamp is preferred because it gives good radiationefficiency.

For promoting the polymerization of the monomers (or oligomers), thecoating liquid (i.e., dispersion of inorganic fine particles containingthe monomers) may be heated. The polymer formed by photopolymerizationmay be further heated to promote thermosetting reaction.

Since the polymer having the anionic group is cross-linked, it isdifficult to regulate its molecular weight.

The amount of the crosslinked polymer having the anionic group in thehigh refractive index layer is in the range of 35 to 95 vol. %,preferably 40 to 90 vol. %, more preferably 44 to 80 vol. %.

Besides the aforementioned components (inorganic fine particles,polymer, disperse medium, polymerization initiator, polymerizationpromoter), the high refractive index layer or the coating liquid for thelayer may contain other agents such as polymerization inhibitor,leveling agent, thickening agent, anti-coloring agent, UV absorber,silane coupling agent, anti-static agent, and adhesion improver.

Examples of the leveling agents include fluorinated alkyl esters (e.g.,FC-430, FC-431 [trade names], Sumitomo 3M Co., Ltd.), and polysiloxanes(e.g., SF1023, SF1054, SF1079 [trade names], General Electric; DC190,DC200, DC510, DC1248 [trade names], Dow Corning; and BYK300, BYK310,BYK320, BYK322, BYK330, BYK370 [trade names], BYK Chemie).

Low Refractive Index Layer

FIG. 3 is a schematic cross-sectional view of a low refractive indexlayer. The upper surface of the low refractive index layer of FIG. 3 isthe surface of the anti-reflection film. A display device or a lens isplaced below the layer of FIG. 3.

As shown in FIG. 3, the low refractive index layer (1) is porous. In thelow refractive index layer (1), the inorganic fine particles (11) havinga mean particle size of 0.5 to 200 nm are piled up (in FIG. 3, threeparticles are piled up). Between the inorganic fine particles (11),micro voids (12) are formed. The low refractive index layer (1) furthercontains polymer (13) in an amount of 5 to 50 wt. %. The polymer (13)combines the particles (11), but does not fills the micro voids (12). Asshown in FIG. 1, the micro voids (12) are preferably not opened butenclosed with the polymer (13) and the inorganic fine particles (11).

The low refractive index layer has a refractive index of 1.20 to 1.55,preferably 1.30 to 1.55, more preferably 1.30 to 1.50, furtherpreferably 1.35 to 1.45.

The thickness of the low refractive index layer is preferably in therange of 50 to 400 nm, more preferably 50 to 200 nm.

The haze of the low refractive index layer is preferably in the range ofnot more than 3%, more preferably not more than 2%, further preferablynot more than 1%.

The low refractive index layer improved according to the invention hasexcellent strength. The layer preferably has a mechanical strength ofnot less than H, more preferably not less than 2H, further preferablynot less than 3H in terms of pencil grades under a load of 1 kgw.

Inorganic Fine Particles in Low Refractive Index Layer

Inorganic fine particles in the low refractive index layer have a meanparticle size of 0.5 to 200 mm. As the particle size increases, forwardscattering of the layer increases. If the particles have a mean particlesize of more than 200 nm, scattered light is colored. Accordingly, themean particle size is preferably in the range of 1 to 100 nm, morepreferably 3 to 70 nm, further preferably 5 to 40 nm. The inorganic fineparticles preferably have uniform sizes (i.e., monodispersed).

The inorganic fine particles in the low refractive index layer arepreferably made of metal oxides, nitrides, sulfides, or halides. Metaloxides and metal halides are preferred, and metal oxides and metalfluorides are particularly preferred. Examples of preferred metalelements include Na, K, Mg, Ca, Ba, Al, Zn, Fe, Cu, Ti, Sn, In, W, Y,Sb, Mn, Ga, V, Nb, Ta, Ag, Si, B, Bi, Mo, Ce, Cd, Be, Pb, and Ni.Further preferred metals are Mg, Ca, B, and Si. Inorganic compoundscontaining two or more metals may be also used.

Particularly preferred inorganic compounds are alkali metal fluorides(e.g., NaF, KF), alkaline earth metal fluorides (e.g., CaF₂, MgF₂), andsilicon dioxide (SiO₂).

The inorganic fine particles in the low refractive index layerpreferably are amorphous.

The inorganic fine particles can be directly prepared in the form ofdispersion by sol-gel method (described in Japanese Patent ProvisionalPublication No. 53-112732, Japanese Patent Publication No. 57-9051) ordeposition method (described in Applied Optics, 27(1988), pp. 3356).Otherwise, the powder obtained by dry-precipitation method may bemechanically pulverized to prepare the dispersion. Commerciallyavailable inorganic fine particles (e.g., sol of silicon dioxide) arealso usable.

For forming the low refractive index layer, the inorganic fine particlesare preferably dispersed in a proper medium. Examples of the mediuminclude water, alcohols (e.g., methanol, ethanol, isopropanol), andketones (e.g., methyl ethyl ketone, methyl isobutyl ketone).

The low refractive index layer contains the inorganic fine particles inan amount of 50 to 95 wt. %, preferably 50 to 90 wt. %, more preferably60 to 90 wt. %, further preferably 70 to 90 wt. %, based on the totalamount of the layer.

Micro Voids in Low Refractive Index Layer

In the low refractive index layer, two or more of the inorganicparticles are piled up to form micro voids between the particles. Thevoid volume is preferably in the range of 3 to 50 vol. %, morepreferably 5 to 35 vol. %.

If globular fine particles having equal sizes (completely monodispersedsizes) are charged in closest packing, the void volume is 26 vol. %. Onthe other hand, the particles of equal sizes charged in primitive cubicpacking give the void volume of 48 vol. %. Since the sizes of practicalparticles are distributed in a certain extent, the low refractive indexlayer practically has a void ratio lower than the above values.

If the void volume (space of micro voids) increases, the refractiveindex of the low refractive index layer decreases. In the invention,since the inorganic fine particles are piled up to form the micro voids,the sizes of the micro voids can be easily controlled at a proper value(a value which neither scatters light nor impairs the mechanicalstrength of the layer) by adjusting the sizes of the particles. Further,by making the sizes of the particles uniform, those of the micro voidscan be also made uniform so as to prepare the low refractive index layerhaving uniform optical characteristics. Thus prepared low refractiveindex layer is microscopically a porous film containing micro voids, butis optically or macroscopically a uniform film.

Owing to the micro voids, the low refractive index layer has amacroscopic refractive index smaller than the total of refractiveindexes of the fine particles and the polymer. The refractive index ofthe layer is a total of the refractive index per volume of eachcomponent, and the refractive indexes of the fine particles and thepolymer are above 1 while that of air is 1.00. Therefore, the microvoids can give the low refractive index layer having a very lowrefractive index.

The micro voids are preferably enclosed with the inorganic fineparticles and the polymer in the low refractive index layer. As comparedwith voids having apertures on the surface of the layer, the enclosedvoids scatter relatively small amount of light.

Polymer in Low Refractive Index Layer

The low refractive index layer contains a polymer in an amount of 5 to50 wt. %. The polymer combines the inorganic fine particles, andsupports the layer containing the micro voids. The amount of the polymeris adjusted so that the micro voids may not be filled with the polymerand so that the layer may have enough strength, and preferably is in therange of 10 to 30 wt. % based on the total amount of the layer.

For combining the inorganic fine particles with the polymer, thefollowing methods are preferred.

(1) The inorganic fine particles are treated with a surface treatmentagent, and then the polymer is combined with the agent on the particles.

(2) Each particle is coated as a core with a shell of the polymer, toform a core-shell structure.

(3) The polymer is used as a binder for the inorganic fine particles.

The polymer (1) combined with the surface treatment agent preferably isthe same as the shell polymer (2) or the binder polymer (3). The shellpolymer (2) is preferably formed around the particles by polymerizationbefore the coating liquid for the low refractive index layer isprepared. For forming the polymer (3), the corresponding monomers areadded into the coating liquid and polymerized during or after applyingthe liquid.

It is preferred to employ two or three of the methods (1) to (3) incombination. The combination of (1) and (3) or that of all the methodsare particularly preferred.

The methods of surface treatment (1), shell polymer (2) and binderpolymer (3) are explained below in this order.

(1) Surface Treatment

The inorganic fine particles are preferably subjected to surfacetreatment, so as to improve affinity to the polymer. The surfacetreatment is categorized into physical treatment (such as plasmatreatment and corona discharge treatment) and chemical treatment withcoupling agents. In the invention, chemical treatment is preferablyperformed singly or in combination with physical treatment. As thecoupling agents, organoalkoxy metal compounds (e.g., titanium couplingagents and silane coupling agents) are preferably used. If the inorganicfine particles are made of silicon dioxide, the surface treatment with asilane coupling agent is particularly preferred.

The silane coupling agents having the following formula (XI-a) or (XI-b)are preferred.

In the formulas, each of R⁶¹, R⁶⁵ and R⁶⁶ independently represents analkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkynylgroup having 2 to 10 carbon atoms or an aralkyl group having 7 to 10carbon atoms; and each of R⁶², R⁶³, R⁶⁴, R⁶⁷ and R⁶⁸ independentlyrepresents an alkyl group having 1 to 6 carbon atoms or an acyl grouphaving 2 to 6 carbon atoms.

In the formulas of (XI-a) and (XI-b), each of R⁶¹, R⁶⁵ and R⁶⁶ ispreferably an alkyl group, an aryl group, an alkenyl group or an aralkylgroup. An alkyl group, an aryl group or an alkenyl group is morepreferred, and an alkyl group or an alkenyl group is further preferred.The alkyl, aryl, alkenyl and aralkyl groups may have one or moresubstituents. Examples of the substituents include glycidyl group,glycidyloxy group, an alkoxy group, a halogen atom, an acyloxy group(e.g., acryloyloxy group, methacryloyloxy group), mercapto group, aminogroup, carboxyl group, cyano group, isocyanato group, and analkenylsulfonyl group (e.g., vinylsulfonyl group).

In the formulas of (XI-a) and (XI-b), each of R⁶², R⁶³, R⁶⁴, R⁶⁷ and R⁶⁸preferably is an alkyl group. The alkyl group may have one or moresubstituents. Examples of the substituents include an alkoxy group.

The silane coupling agent preferably comprises a double bond, and thepolymer is combined with the coupling agent by the reaction of thedouble bond. The double bond preferably is in the substituent of R⁶¹,R⁶⁵ or R⁶⁶ in the formulas of (XI-a) and (XI-b).

The silane coupling agents having the following formula (XII-a) or(XII-b) are particularly preferred.

In the formulas, each of R⁷¹ and R⁷⁵ independently represents hydrogenatom or methyl group; R⁷⁶ represents an alkyl group having 1 to 10carbon atoms, an aryl group having 6 to 10 carbon atoms, an alkenylgroup having 2 to 10 carbon atoms, an alkynyl group having 2 to 10carbon atoms or an aralkyl group having 7 to 10 carbon atoms; each ofR⁷², R⁷³, R⁷⁴, R⁷⁷ and R⁷⁸ independently represents an alkyl grouphaving 1 to 6 carbon atoms or an acyl group having 2 to 6 carbon atoms;and each of L⁷¹ and L⁷² independently represents a divalent linkinggroup.

In the formula of (XII-b), R⁷⁶ is the same as R⁶¹, R⁶⁵ and R⁶⁶ in theformulas of (XI-a) and (XI-b).

In the formulas of (XII-a) and (XII-b), R⁷², R⁷³, R⁷⁴, R⁷⁷ and R⁷⁸ arethe same as R⁶², R⁶³, R⁶⁴, R⁶⁷ and R⁶⁸ in the formulas of (XI-a) and(XI-b), respectively.

In the formulas of (XII-a) and (XII-b), each of L⁷¹ and L⁷² ispreferably an alkylene group, more preferably an alkylene group having 1to 10 carbon atoms, further preferably an alkylene group having 1 to 6carbon atoms.

Examples of the silane coupling agents having the formula (XI-a) includemethyltrimethoxysilane, methyltriethoxysilane,methyltrimethoxyethoxysilane, methyltriacetoxysilane,methyltributoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane,vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane,vinyltrimethoxyethoxysilane, phenyltrimethoxysilane,phenyltriethoxysilane, phenyltriacetoxysilane,γ-chloropropyltrimethoxysilane, γ-chloropropyltriethoxysilane,γ-chloropropyltriacetoxysilane, 3,3,3-trifluoropropyltriethoxysilane,γ-glycidyloxypropyltrimethoxysilane, γ-glycidyloxypropyltriethoxysilane,γ-(β-glycidyloxyethoxy)propyltrimethoxysilane,β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,β-(3,4-epoxycyclohexyl)ethyltriethoxysilane,γ-acryloyloxypropyltrimethoxysilane,γ-methacryloyloxypropyltrimethoxysilane, γ-aminopropyltrimethoxysilane,γ-aminopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane,γ-mercaptopropyltriethoxysilane,N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, andβ-cyanoethyltriethoxysilane.

Preferred examples are those having a double bond such asvinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane,vinyltrimethoxyethoxysilane, γ-acryloyloxypropyltrimethoxysilane,γ-methacryloyloxypropyltrimethoxysilane. The silane coupling agentshaving the formula (XII-a) such as γ-acryloyloxypropyltrimethoxysilaneand γ-methacryloyloxypropyltrimethoxysilane are particularly preferred.

Examples of the silane coupling agents having the formula (XI-b) includedimethyldimethoxysilane, phenylmethyldimethoxysilane,dimethyldiethoxysilane, phenylmethyldiethoxysilane,γ-glycidyloxypropylmethyldiethoxysilane,γ-glycidyloxypropylmethyldimethoxysilane,γ-glycidyloxypropylphenyldiethoxysilane,γ-chloropropylmethyldiethoxysilane, dimethyldiacetoxysilane,γ-acryloyloxypropylmethyldimethoxysilane,γ-acryloyloxypropylmethyldiethoxysilane,γ-methacryloyloxypropylmethyldimethoxysilane,γ-methacryloyloxypropylmethyldiethoxysilane,γ-mercaptopropylmethyldimethoxysilane,γ-mercaptopropylmethyldiethoxysilane,γ-aminopropylmethyldimethoxysilane, γ-aminopropylmethyldiethoxysilane,methylvinyldimethoxysilane, and methylvinyldiethoxysilane.

Preferred examples are those having a double bond such asγ-acryloyloxypropylmethyldimethoxysilane,γ-acryloyloxypropylmethyldiethoxysilane,γ-methacryloyloxypropylmethyldimethoxysilane,γ-methacryloyloxypropylmethyldiethoxysilane, methylvinyldimethoxysilane,and methylvinyldiethoxysilane. The silane coupling agents having theformula (XII-b) such as γ-acryloyloxypropylmethyldimethoxysilane,γ-acryloyloxypropylmethyldiethoxysilane,γ-methacryloyloxypropylmethyldimethoxysilane andγ-methacryloyloxypropylmethyldiethoxysilane are particularly preferred.

Two or more coupling agents may be used in combination. In combinationwith the silane coupling agents having the formula (XI-a) or (XI-b),other silane coupling agents may be used. Examples of other silanecoupling agents include orthosilicic alkyl esters (e.g., methylorthosilicate, ethyl orthosilicate, n-propyl orthosilicate, i-propylorthosilicate, n-butyl orthosilicate, sec-butyl orthosilicate, t-butylorthosilicate), and their hydrolyzed products.

The surface treatment with a silane coupling agent comprises the stepsof adding the coupling agent to the dispersion of the inorganicparticles, and storing the dispersion at a temperature of roomtemperature to 60° C. for a period of several hours to 10 days. Foraccelerating the treatment, inorganic acids (e.g., sulfuric acid,hydrochloric acid, nitric acid, chromic acid, hypochlorous acid, boricacid, orthosilicic acid, phosphoric acid, carbonic acid), organic acids(e.g., acetic acid, polyacrylic acid, benzenesulfonic acid, phenol,polyglutamic acid) or their salts (e.g., metallic salts, ammonium salts)may be added to the dispersion.

(2) Shell Polymer

The polymer for shell preferably has a main chain of saturatedhydrocarbon. Further, the polymer preferably has fluorine atoms in themain chain or side chain, more preferably in the side chain. Preferredexamples of the polymer include polyacrylic esters and polymethacrylicesters. Esters between fluorinated alcohols and poly(meth)acrylic acidare particularly preferred.

The refractive index of shell polymer decreases as the fluorine contentin the polymer increases. For depressing the refractive index of the lowrefractive index layer, the shell polymer preferably contains fluorinein an amount of 35 to 80 wt. %, more preferably 45 to 75 wt. %.

The polymer containing fluorine atoms is preferably prepared bypolymerization of an ethylenic unsaturated monomer having a fluorineatom. Examples of the ethylenic unsaturated monomers having fluorineatom include fluoroolefins (e.g., fluoroethylene, vinylidene fluoride,tetrafluoroethylene, hexafluoropropylene, andperfluoro-2,2-dimethyl-1,3-dioxol), fluorinated vinylether, and estersbetween fluorinated alcohols and (meth)acrylic acid.

The polymer containing fluorine atoms particularly preferably comprisesthe following repeating unit (XIII) containing fluorine atoms.

In the formula, R⁸¹ represents hydrogen atom or fluorine atom; p is 0 ora positive integer; and n is a positive integer.

The shell polymer may be a copolymer comprising repeating units havingfluorine atoms and ones having no fluorine atom. The repeating unitshaving no fluorine atom are preferably prepared by polymerization of anethylenic unsaturated monomer having no fluorine atom. Examples of theethylenic unsaturated monomers having no fluorine atom include olefins(e.g., ethylene, propylene, isoprene, vinyl chloride, and vinylidenechloride), acrylic esters (e.g., methyl acrylate, ethyl acrylate, an2-ethylhexyl acrylate), methacrylic esters (e.g., methyl methacrylate,ethyl methacrylate, butyl methacrylate, and ethylene glycoldimethacrylate), styrene and its derivatives (e.g., styrene,divinylbenzene, vinyltoluene, and α-methylstyrene), vinyl ethers (e.g.,methylvinyl ether), vinyl esters (e.g., vinyl acetate, vinyl propionate,and vinyl cinnamate), acrylamides (e.g., N-tert-butylacrylamide andN-cyclohexylacrylamide), methacrylamide, and acrylonitrile.

If the binder polymer (3) described below is used in combination, theshell polymer and the binder polymer may be chemically combined withcrosslinking. The crosslinking can be formed by introducingcrosslinkable functional groups into the shell polymer.

The shell polymer may be crystalline. If the shell polymer has a glasstransition temperature (Tg) higher than the temperature at which the lowrefractive index layer is formed, the micro voids in the layer areeasily maintained. However, in that case, the inorganic fine particlesare often insufficiently combined, and consequently the low refractiveindex layer can not be formed as a continuous layer (consequently, theresultant layer has insufficient mechanical strength). Accordingly, thebinder polymer (3) described below is preferably used in combination, soas to form a continuous low refractive index layer.

Core-shell fine particles are prepared by forming polymer shells aroundthe inorganic fine particles. The core-shell fine particles preferablycontain cores of the inorganic fine particles in an amount of 5 to 90vol. %, more preferably 15 to 80 vol. %.

The polymer shell is preferably formed by radical polymerization. Theradical polymerization is described in “Experimental method of polymersynthesis” written by T.Ohtsu and M.Kinoshita, published by Kagakudojin(1972); and “Lectures, Polymerization Reaction, Radical Polymerization(I)” written by T.Ohtsu, published by Kagakudojin (1971). The radicalpolymerization is preferably performed in accordance with emulsionpolymerization method or dispersion polymerization method, which aredescribed in “Chemistry of Polymer Latex” written by S.Muroi, publishedby Kobunshi-kankokai (1970) and “Dispersion Polymerization in OrganicMedia” written by Barrett and Keih E. J., published by John Willey &Sons (1975).

Examples of initiators for the emulsion polymerization include inorganicperoxides (e.g., potassium persulfate, ammonium persulfate), azonitriles(e.g., sodium azobiscyanovalerate), azoamidine compounds (e.g.,2,2′-azobis(2-methylpropionamide) hydrochloride), cyclic azoamidinecompounds (e.g., 2,2′-azobis(2-(5-methyl-2-imidazolin-2-yl)propanehydrochloride), azoamide compounds (e.g.,2,2′-azobis{2-methyl-N-[1,1′-bis(hydroxymethyl)-2-hydroxyethyl]propioneamide). Inorganic peroxides are preferred, and potassium persulfate andammonium persulfate are particularly preferred.

Examples of initiators for the dispersion polymerization include azocompounds (e.g., 2,2′-azobisisobutylonitrile,2,2′-azobis(2,4-dimethylvaleronitrile),dimethyl-2,2′-azobis(2-methylpropionate),dimethyl-2,2′-azobisisobutylate), and organic peroxides (e.g., laurylperoxide, benzoyl peroxide, and tert-butylperoctoate).

The dispersion polymerization method preferably comprises the steps ofmixing a dispersing agent of polymer and the surface-treated inorganicfine particles, adding the monomers and the initiator to the mixture,and polymerizing the monomers in a medium which does not dissolve theformed polymer.

Examples of the medium include water, alcohols (e.g., methanol, ethanol,propanol, isopropanol, 2-methoxy-1-propanol, butanol, t-butanol,pentanol, neopentanol, cyclohexanol, 1-methoxy-2-propanol), methyl ethylketone, acetonitrile, tetrahydrofuran, and ethyl acetate. Preferred arewater, methanol, ethanol and isopropanol. Two or more media may be usedin combination.

In the emulsion or dispersion polymerization method, chain transferagents may be used. Examples of the chain transfer agents includehalogenated hydrocarbons (e.g., carbon tetrachloride, carbontetrabromide, ethyl acetate dibromide, ethyl acetate tribromide,ethylbenzene dibromide, ethane dibromide, and ethane dichloride),hydrocarbons (e.g., benzene, ethylbenzene, and isopropylbenzene),thioethers (e.g., diazothioether), mercaptans (e.g., t-dodecylmercaptan, n-dodecyl mercaptan, hexadecyl mercaptan, n-octadecylmercaptan, and thioglycerol), disulfides (e.g.,diisopropylxanthogendisulfide), thioglycollic acid and its derivatives(e.g., thioglycolic acid, 2-ethylhexyl thioglycolate, butylthioglycolate, methoxybutyl thioglycolate, and trimethylolpropanetris(thioglycolate)).

Two or more kinds of core-shell fine particles may be used incombination. Further, the core-shell fine particles may be used incombination with inorganic fine particles having no shells.

(3) Binder Polymer

The binder polymer preferably has a main chain of saturated hydrocarbonor polyether, more preferably a main chain of saturated hydrocarbon.Preferably, the binder polymer is crosslinked.

The polymer having a main chain of saturated hydrocarbon is preferablyprepared by polymerization of ethylenic unsaturated monomers. Forpreparing a crosslinked binder polymer, monomers having two or moreethylenic unsaturated groups are preferably used.

Examples of the monomer having two or more ethylenic unsaturated groupsinclude esters of polyhydric alcohols and (meth)acrylic acid (e.g.,ethyleneglycol di(meth)acrylate, 1,4-cyclohexane diacrylate,pentaerythritol tetra(meth)acrylate, pentaerythritol tri(meth)acrylate,trimethylolpropane tri(meth)acrylate, trimethylolethanetri(meth)acrylate, dipentaerythritol tetra(meth)acrylate,dipentaerythritol penta(meth)acrylate, pentaerythritolhexa(meth)acrylate, 1,2,3-cyclohexanetetramethacrylate, polyurethanepolyacrylate, and polyester polyacrylate), and vinylbenzene and itsderivatives (e.g., 1,4-divinylbenzene, 4-vinylbenzoicacid-2-acryloylethyl ester and 1,4-divinylcyclohexanone), vinylsulfones(e.g., divinylsulfone), acrylamides (e.g., methylene bisacrylamide), andmethacrylamide.

The polymer having a main chain of polyether is preferably prepared byring-opening polymerization of multi-functional epoxy compounds.

In place of or in addition to the monomer having two or more ethylenicunsaturated groups, crosslinking groups may be incorporated into thebinder polymer to form a crosslinked structure. Examples of thecrosslinking functional groups include isocyanato group, epoxy group,aziridine group, oxazoline group, aldehyde group, carbonyl group,hydrazine group, carboxyl group, methylol group, and active methylenegroup. Further, vinylsulfonic acid, acid anhydrides, cyanoacrylatederivatives, melamine, etherized methylol, esters, and urethane are alsoemployable as monomers for forming the crosslinked structure. Thefunctional groups, such as block isocyanate group, decomposed to formthe crosslinked structure are also employable.

The term of “crosslinking groups” in the invention is not used torestrict by the aforementioned compounds, and include the groupsdecomposable to give an active compound.

If the binder polymer is used in combination with the shell polymer (2),the glass transition temperature (Tg) of the binder polymer preferablyis lower than that of the shell polymer. The difference between thoseglass transition temperatures preferably is not less than 5° C., morepreferably not less than 20° C.

The binder polymer is preferably prepared by the steps of adding themonomers to the coating liquid for the low refractive index layer, andpolymerizing (and if needed crosslonking) the monomers during or afterapplying the liquid. Examples of the polymerization initiator for thebinder polymer are the same as those descried for the shell polymer. Inthe coating liquid for low refractive index layer, a small amount ofpolymer (such as polyvinyl alcohol, polyoxyethylene,polymethylmethacrylate, polymethylacrylate, diacetylcellulose,triacetylcellulose, nitrocellulose, polyester, or alkyd resin) may beadded.

Transparent Support

Except the case that the anti-reflection film is directly provided on alens or a display screen of CRT, the film is preferably provided on atransparent support. As the support, a plastic film is more preferablethan a glass plate.

Examples of the plastic materials for the support include cellulosederivatives (e.g., diacetyl cellulose, triacetyl cellulose, propionylcellulose, butyryl cellulose, acetyl propionyl cellulose, andnitrocellulose), polyamides, polycarbonates, polyesters (e.g.,polyethylene terephthalate, polyethylene naphthalate, polybutyleneterephthalate, poly-1,4-cyclohexanedimethylene terephthalate, andpolyethylene-1,2-diphenoxyethane-4,4′-dicarboxylate), polystyrene (e.g.,syndiotactic polystyrene), polyolefins (e.g., polypropylene,polyethylene and polymethylpentene), polymethyl methacrylate,polysulfone, polyethersulfone, polyarylate, polyether ketone, andpolyether imide. Triacetyl cellulose, polycarbonates, and polyethyleneterephthalate are preferred.

The transparent support preferably has a percent transmission of notless than 80%, more preferably not less than 86%. The haze of thesupport is preferably in the range of not more than 2.0%, morepreferably not more than 1.0%. The support preferably has a refractiveindex of 1.4 to 1.7.

IR absorbers or UV absorbers may be incorporated into the transparentsupport. The amount of the IR absorber is preferably in the range of0.01 to 20 wt. %, more preferably 0.05 to 10 wt. %. As a slipping agent,particles of inactive inorganic compound may be contained in thetransparent support. Examples of the inorganic compound include SiO₂,TiO₂, BaSO₄, CaCO₃, talc, and kaolin.

The transparent support may be subjected to surface treatment. Examplesof the surface treatments include chemical treatment, mechanicaltreatment, corona discharge treatment, flame treatment, UV treatment,high frequency treatment, glow discharge treatment, active plasmatreatment, laser treatment, mix acid treatment, and ozone-oxidationtreatment. Preferred treatments are glow discharge treatment, UVtreatment, corona discharge treatment, and flame treatment. Glowdischarge treatment and UV treatment are particularly preferred.

Middle Refractive Index Layer

As shown in FIG. 1(c), a middle refractive index layer may be providedbetween the high refractive index layer and the transparent support. Therefractive index of the middle refractive index layer is adjusted to avalue between those of the high and low refractive index layers, andpreferably is in the range of 1.55 to 1.70.

The middle refractive index layer is preferably formed with a polymerhaving a relatively high refractive index. Examples of the polymerhaving a high refractive index include polystyrene, styrene copolymer,polycarbonate, melamine resin, phenol resin, epoxy resin, andpolyurethane derived from the reaction between cyclic (alicyclic oraromatic) isocyanate and polyol. Further, other polymers having cyclic(aromatic, heterocyclic, or alicyclic) groups and polymers substitutedwith a halogen atom other than fluorine also have a high refractiveindex. The polymer may be prepared by polymerization of a monomer havingdouble bond for radical hardening.

In the polymer, inorganic fine particles having a high refractive indexmay be dispersed. If those particles are used, even polymers having arelatively low refractive index can be used for dispersing the particlesstably. Examples of those polymers include vinyl polymers (includingacrylic polymers), polyester polymers (including alkyd polymer),cellulose polymers, and urethane polymers.

The middle refractive index layer may contain silicon compoundssubstituted with organic groups. As the silicon compounds, theaforementioned silane coupling agents and its derivatives for surfacetreatment of the inorganic fine particles in the low refractive indexlayer are preferably employed.

As the material of the inorganic fine particles in the middle refractiveindex layer, oxides of metals (e.g., aluminum, titanium, zirconium,antimony) are preferred. Powder or colloidal dispersion of the particlesis mixed with the polymer or the organic silicon compounds.

The inorganic fine particles preferably has a mean particle size of 10to 100 nm.

The middle refractive index layer may be formed of film-formableorganometallic compounds. Preferably, the organometallic compounds areliquids or can be dispersed in a proper medium.

Examples of the organometallic compounds include metal alcoholates(e.g., titanium tetraethoxide, titanium tetra-i-propoxide, titaniumtetra-n-propoxide, titanium tetra-n-butoxide, titaniumtetra-sec-butoxide, titanium tetra-tert-butoxide, aluminum triethoxide,aluminum tri-i-propoxide, aluminum tributoxide, antimony triethoxide,antimony tri-butoxide, zirconium tetraethoxide, zirconiumtetra-i-propoxide, zirconium tetra-n-propoxide, zirconiumtetra-n-butoxide, zirconium tetra-sec-butoxide, zirconiumtetra-tert-butoxide), chelate compounds (e.g., di-isopropoxy titaniumbisacetylacetonate, di-butoxy titanium bisacetylacetonate, di-ethoxytitanium bisacetylacetonate, bis-acetylacetone zirconium, aluminumacetylacetonate, aluminum di-n-butoxidemonoethylacetonate, aluminumdi-i-propoxide-monomethylacetoacetate, tri-n-butoxidezirconiummonoethylacetate), organic acid salts (e.g., zirconium ammoniumcarbonate), and active inorganic polymers mainly comprising zirconium.

The middle refractive index layer may contain alkyl silicates, theirhydrolyzed products, and fine particles of silica, particularlycolloidal dispersion of silica-gel.

The haze of the middle refractive index layer preferably is not morethan 3%.

Other Layers

Besides the aforementioned layers, the anti-reflection film may haveother layers such as a hard coating layer, a moisture proof layer, anantistatic layer, an undercoating layer, and a protective layer.

The hard coating layer gives scratch resistance, and further enhancesadhesion between the transparent support and the layer provided thereon.The hard coating layer can be formed of acrylic polymers, urethanepolymers, epoxy polymers, silicon polymers, or silica compounds.Pigments may be added to the hard coating layer.

The acrylic polymers are preferably prepared by polymerization ofmulti-functional monomers (e.g., polyol acrylate, polyester acrylate,urethane acrylate, and epoxy acrylate). Examples of the urethanepolymers include melamine polyurethane. Preferred examples of thesilicon polymers include products derived from co-hydrolysis betweensilane compounds (e.g., tetraalkoxysilane and alkyltrialkoxysilane), andsilane coupling agents having active groups (e.g., epoxy, methacryl).Two or more polymers may be used in combination. As the silica compound,colloidal silica is preferably used. The hard coating layer preferablyhas a mechanical strength of not less than H, more preferably not lessthan 2H, further preferably not less than 3H in terms of pencil gradesunder a load of 1 kgw.

In addition to the hard coating layer, other layers such as an adhesivelayer, a shielding layer, a slippery layer and an antistatic layer maybe also provided on the transparent support. The shielding layerprotects the film from electromagnetic waves such as infrared rays.

A protective layer may be provided on the low refractive index layer.The protective layer also serves as a slippery layer or a anti-stainlayer.

Examples of slipping agents for the slippery layer includepolyorganosiloxanes (e.g., polydimethylsiloxane, polydiethylsiloxane,polydiphenylsiloxane, polymethylphenylsiloxane, and alkyl-modifiedpolydimethylsiloxane), natural waxes (e.g., carnauba wax, candelillawax, jojoba oil, rice wax, Japan wax, bees wax, hydrous lanolin,spermaceti, and montan wax), petroleum waxes (e.g., paraffin wax andmicrocrystalline wax), synthetic waxes (e.g., polyethylene wax andFischer-Tropsch wax), higher fatty acid amides (e.g., stearamide, oleicamide, and N,N′-methylenebisstearamide), higher fatty acid esters (e.g.,methyl stearate, butyl stearate, glycerol monostearate, and sorbitanmonooleate), higher fatty acid metal salts (e.g., zinc stearate), andpolymers containing fluorine (e.g., perfluoropolyether having aperfluoro main chain, perfluoropolyether having a perfluoro side chain,perfluoropolyether modified with alcohol, and perfluoropolyethermodified with isocyanate).

The anti-stain layer contains hydrophobic compounds containing fluorine(e.g., polymer containing fluorine, surface active agent containingfluorine, oil containing fluorine).

The protective layer has a thickness of not more than 20 nm, preferably2 to 20 nm, more preferably 3 to 20 nm, further preferably 5 to 10 nm,so as not to affect the performance of anti-reflection.

Anti-reflection Film

Each layer of the anti-reflection film can be formed by dip coating, airknife coating, curtain coating, roller coating, wire bar coating,gravure coating, and extrusion coating (described in U.S. Pat. No.2,681,294). Two or more layers may be simultaneously formed by coating.The method for simultaneous coating is described in U.S. Pat. Nos.2,761,791, 2,941,898, 3,508,947, and 3,526,528; and “CoatingEngineering” pp.253, written by Y. Harazaki, published by Asakura Shoten(1973).

The anti-reflection film may have anti-glare function, which means thatthe film may be made to scatter external light. For the anti-glarefunction, small convexes are formed on the surface of the film. As shownin FIG. 3, a low refractive index layer containing fine particles has asurface having convexes formed with the particles. If those convexesgive insufficient anti-glare function, relatively large particles(having a mean particle size of 50 nm to 2 um) may be incorporated in asmall amount (0.1 to 50 wt. %).

The haze of the anti-reflection film is preferably in the range of 3 to30%, more preferably 5 to 20%, further preferably 7 to 20%.

The anti-reflection film of the invention can be applied on a displaydevice such as a liquid crystal display (LCD), a plasma display (PDP),an electroluminescence display (ELD) or a cathode ray tube display(CRT). If the film has a transparent support, the support is attached tothe display surface. The film can be also placed on a case cover, anoptical lens, a lens for glasses, a windshield, a light cover, and acover of helmet.

EXAMPLE 1 Preparation of Titanium Dioxide Dispersion

Thirty weight parts of titanium dioxide [weight mean particle size ofprimary particles: 50 nm, refractive index: 2.70], 3 weight parts of thefollowing anionic monomer (1), 3 weight parts of the following anionicmonomer (2), and 64 weight parts of methyl ethyl ketone were mixed bymeans of a sand grinder to prepare a dispersion of titanium dioxide.

The weight mean particle size of titanium dioxide in the prepareddispersion was determined by means of a coaltar counter. The results areshown in Table 1.

Preparation of Coating Liquid for High Refractive Index Layer

A mixture of dipentaerythritol pentaacrylate and dipentaerythritolhexaacrylate [DPHA, Nippon Kayaku Co., Ltd.], a photopolymerizationinitiator [Irgacure 907, Ciba-Geigy], a photosensitizer [Kayacure DETX,Nippon Kayaku Co., Ltd.], and methyl ethyl ketone were mixed. The weightratio of the photopolymerization initiator to the photosensitizer wasset at 3/1, and the volume ratio of the titanium dioxide to the monomers(i.e., the total amount of dipentaerythritol pentaacrylate,dipentaerythritol hexaacrylate, and the anionic monomers (1) and (2))was set at 40/60. The total amount of the photopolymerization initiatorand the photosensitizer was adjusted to 3 wt. % based on the totalamount of the monomers.

The dispersion stability of titanium dioxide in the prepared coatingliquid was evaluated by the following precipitation test. After storingfor 100 hours, the nature of the liquid was determined according towhether the clear top part was observed or not. The marke “A” means thatthe clear top part was not observed, and the mark of “B” means that itwas observed. The results are shown in Table 1.

Formation of High Refractive Index Layer

On a polyethylene terephthalate film having 90 μm thickness, a hardcoating layer was provided. The coating liquid for high refractive indexlayer was applied on the hard coating layer with a bar coater, andirradiated with UV light to harden. Thus, a high refractive index layerhaving 200 nm thickness (aftre dryness) was formed.

The haze of the formed layer was measured by means of a haze meter(NDH-1001DP, Nippon Denshoku Kogyo Co., Ltd.), and the refractive indexwas calculated from the reflectance measured with a reflectance meter(V-550 and ARV-474, Nippon Bunko Co., Ltd.). Further, the mechanicalstrength was evaluated in terms of pencil hardness (under a load of 1kgw). The results are set forth in Table 1.

Formation of Low Refractive Index Layer

Six g of dipentaerythritol hexaacrylate, 0.5 g of a photopolymerizationinitiator [Irgacure 907, Ciba-Geigy], 0.2 g of a photosensitizer[Kayacure DETX, Nippon Kayaku Co., Ltd.], and 20 g of ethyl acetate weredispersed and emulsified in 100 g of water with 1 g of sodiumdodecybenzene sulfonate. The emulsified liquid and 100 g of fineparticles (mean particle size: 52 nm) of copolymer of methylmethacrylate (80 weight parts)-divinylbenzene (25 weight parts) weremixed and stirred to form a coating liquid for low refractive indexlayer.

The coating liquid was applied on the high refractive index layer with abar coater to form a layer having the thickness of 100 nm. After drying,the layer was heated to 100° C., and irradiated with UV light of a 12W/cm high pressure mercury lamp for 1 minute to crosslink the polymer.The layer was cooled to room temperature, so as to form a low refractiveindex layer (refractive index: 1.55).

Thus, an anti-reflection film was produced.

COMPARISON EXAMPLE 1

30 weight parts of titanium dioxide [weight mean particle size ofprimary particles: 50 nm, refractive index: 2.70] and 64 weight parts ofmethyl ethyl ketone were mixed by means of a sand grinder to prepare adispersion of titanium dioxide.

Except for using thus prepared dispersion, the procedure of Example 1was repeated to produce an anti-reflection film and to evaluate thefilm. The results are set forth in Table 1.

COMPARISON EXAMPLE 2

30 weight parts of titanium dioxide [weight mean particle size ofprimary particles: 50 nm, refractive index: 2.70], 6 weight parts of aphosphoric surface active agent [Phosphanol RD-720, Toho Kagaku KogyoCo., Ltd.], and 64 weight parts of methyl ethyl ketone were mixed bymeans of a sand grinder to prepare a dispersion of titanium dioxide.

Except for using thus prepared dispersion, the procedure of Example 1was repeated to produce an anti-reflection film and to evaluate thefilm. The results are set forth in Table 1.

COMPARISON EXAMPLE 3

30 weight parts of titanium dioxide [weight mean particle size ofprimary particles: 50 nm, refractive index: 2.70], 1.5 weight parts of aphosphoric surface active agent [Phosphanol RD-720, Toho Kagaku KogyoCo., Ltd.], and 68.5 weight parts of methyl ethyl ketone were mixed bymeans of a sand grinder to prepare a dispersion of titanium dioxide.

Except for using thus prepared dispersion, the procedure of Example 1was repeated to produce an anti-reflection film and to evaluate thefilm. The results are set forth in Table 1.

EXAMPLE 2

30 weight parts of titanium dioxide [weight mean particle size ofprimary particles: 50 nm, refractive index: 2.70], 6 weight parts of thefollowing anionic monomer (3), and 64 weight parts of methyl ethylketone were mixed by means of a sand grinder to prepare a dispersion oftitanium dioxide.

Except for using thus prepared dispersion, the procedure of Example 1was repeated to produce an anti-reflection film and to evaluate thefilm. The results are set forth in Table 1.

EXAMPLE 3

30 weight parts of tin oxide [weight mean particle size of primaryparticles: 10 nm, refractive index: 2.00], 3 weight parts of the anionicmonomer (1) in Example 1, 3 weight parts of the anionic monomer (2) inExample 1, and 64 weight parts of methyl ethyl ketone were mixed bymeans of a sand grinder to prepare a dispersion of tin oxide.

Except for using thus prepared tin oxide dispersion in place of titaniumdioxide dispersion, the procedure of Example 1 was repeated to producean anti-reflection film and to evaluate the film. The results are setforth in Table 1.

EXAMPLE 4

30 weight parts of titanium dioxide [weight mean particle size ofprimary particles: 110 nm, refractive index: 2.70], 6 weight parts ofthe following anionic monomer (4), and 64 weight parts of methyl ethylketone were mixed by means of a sand grinder to prepare a dispersion oftitanium dioxide.

Except for using thus prepared dispersion, the procedure of Example 1was repeated to produce an anti-reflection film and to evaluate thefilm. The results are set forth in Table 1.

COMPARISON EXAMPLE 4

30 weight parts of titanium dioxide [weight mean particle size ofprimary particles: 200 nm, refractive index: 2.70], 3 weight parts ofthe anionic monomer (1) in Example 1, 3 weight parts of the anionicmonomer (2) in Example 1, and 64 weight parts of methyl ethyl ketonewere mixed by means of a sand grinder to prepare a dispersion oftitanium dioxide.

Except for using thus prepared dispersion, the procedure of Example 1was repeated to produce an anti-reflection film and to evaluate thefilm. The results are set forth in Table 1.

EXAMPLE 5

30 weight parts of tin oxide [weight mean particle size of primaryparticles: 10 nm, refractive index: 2.00], 6 weight parts of thefollowing anionic monomer (5), and 64 weight parts of methyl ethylketone were mixed by means of a sand grinder to prepare a dispersion oftin oxide.

anionic monomer (5)

To thus prepared dispersion, glycerol dimethacrylate (Blemmer GMR,Nippon Yushi Co., Ltd.), a photopolymerization initiator [Irgacure 907,Ciba-Geigy], a photosensitizer [Kayacure DETX, Nippon Kayaku Co., Ltd.],and methyl ethyl ketone were added. The weight ratio of thephotopolymerization initiator to the photosensitizer was set at 3/1, andthe volume ratio of the tin oxide to the monomers (i.e., the totalamount of glycerol dimethacrylate and the anionic monomer (5)) was setat 40/60. The total amount of the photopolymerization initiator and thephotosensitizer was adjusted to 3 wt. % based on the total amount of themonomers.

Except for using thus prepared coating liquid for high refractive indexlayer, the procedure of Example 1 was repeated to produce ananti-reflection film and to evaluate the film. The results are set forthin Table 1

EXAMPLE 6

30 weight parts of tin oxide [weight mean particle size of primaryparticles: 10 nm, refractive index: 2.00], 6 weight parts of thefollowing anionic monomer (6), and 64 weight parts of methyl ethylketone were mixed by means of a sand grinder to prepare a dispersion oftin oxide.

anionic monomer (6)

To the tin oxide dispersion, the following epoxy cyclohexane monomer[Eripord GT300, Daicel Chemical Industries Ltd.], the following aromaticsulfonium salt (photopolymerization initiator), and methyl ethyl ketonewere added. The volume ratio of the tin oxide to the monomers (i.e., thetotal amount of the epoxy cyclohexanic monomer and the anionic monomer(6)) was set at 40/60. The amount of the aromatic sulfonium salt wasadjusted to 3 wt. % based on the total amount of the monomers.

On a polyethylene terephthalate film having 90 μm thickness, a hardcoating layer was provided. The prepared coating liquid for highrefractive index layer was applied on the hard coating layer with a barcoater, irradiated with UV light and heated to harden. Thus, a highrefractive index layer having 200 nm thickness (after dryness) wasformed.

On thus formed high refractive index layer, a low refractive index layeris provided in the manner of Example 1 to produce an anti-reflectionfilm. The film was then evaluated, and the results are set forth inTable 1.

EXAMPLE 7

30 weight parts of titanium dioxide [weight mean particle size ofprimary particles: 30 nm, refractive index: 2.70], 6 weight parts of thefollowing anionic monomer (7), 1 weight part of n-octylamine, and 63weight parts of methyl ethyl ketone were mixed by means of a sandgrinder to prepare a dispersion of titanium dioxide.

anionic monomer (7)

To the dispersion of titanium dioxide, a mixture of dipentaerythritolpentaacrylate and dipentaerythritol hexaacrylate [DPHA, Nippon KayakuCo., Ltd.], a photopolymerization initiator [Irgacure 907, Ciba-Geigy],a photosensitizer [Kayacure DETX, Nippon Kayaku Co., Ltd.], and methylethyl ketone were added. The weight ratio of the photopolymerizationinitiator to the photosensitizer was set at 3/1, and the volume ratio ofthe titanium dioxide to the monomers (i.e., the total amount ofdipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, and theanionic monomer (7)) was set at 48/52. The total amount of thephotopolymerization initiator and the photosensitizer was adjusted to 3wt. % based on the total amount of the monomers.

Except for using thus prepared coating liquid for high refractive indexlayer, the procedure of Example 1 was repeated to produce ananti-reflection film and to evaluate the film. The results are set forthin Table 1.

EXAMPLE 8

30 weight parts of titanium dioxide [weight mean particle size ofprimary particles: 50 nm, refractive index: 2.70], 3 weight parts ofanionic monomer (1) in Example 1, 3 weight parts of anionic monomer (2)in Example 1, 1 weight part of the following cationic monomer, and 63weight parts of methyl ethyl ketone were mixed by means of a sandgrinder to prepare a dispersion of titanium dioxide.

cationic monomer

To the dispersion of titanium dioxide, a mixture of dipentaerythritolpentaacrylate and dipentaerythritol hexaacrylate [DPHA, Nippon KayakuCo., Ltd.], a photopolymerization initiator [Irgacure 907, Ciba-Geigy],a photosensitizer [Kayacure DETX, Nippon Kayaku Co., Ltd.], and methylethyl ketone were added. The weight ratio of the photopolymerizationinitiator to the photosensitizer was set at 3/1, and the volume ratio ofthe titanium dioxide to the monomers (i.e., the total amount ofdipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, theanionic monomers (1) and (2), and the cationic monomer) was set at51/49. The total amount of the photopolymerization initiator and thephotosensitizer was adjusted to 3 wt. % based on the total amount of themonomers.

Except for using thus prepared coating liquid for high refractive indexlayer, the procedure of Example 1 was repeated to produce ananti-reflection film and to evaluate the film. The results are set forthin Table 1.

TABLE 1 polymer in high re- particles fractive index layer γ* δ* ε* hazeα* β* Ex.1 anionic crosslinked. Ti 65 A 0.3% 2.02 3H CE.1 crosslinked Ti253 B 33% —** 3H CE.2 crosslinked/surface active agent Ti 67 A 0.3% 1.994B CE.3 crosslinked/surface active agent Ti 205 B 30% −** B Ex.2 anioniccrosslinked Ti 43 A 0.1% 1.83 3H Ex.3 anionic crosslinked Sn 35 A 0.1%1.70 3H Ex.4 anionic crosslinked Ti 115 A 0.5% 1.65 3H CE.4 anioniccrosslinked Ti 215 A 17% −** 3H Ex.5 anionic crosslinked Sn 35 A 0.1%1.71 3H Ex.6 anionic crosslinked Sn 35 A 0.1% 1.72 3H Ex.7 anioniccrosslinked Ti 43 A 0.2% 2.12 3H Ex.8 amphoteric crosslinked Ti 65 A0.2% 2.18 3H Remarks: *) each of α, β, γ, δ and ε is as follows. α:refractive index, β: mechanical strength, γ: material of the particles,δ: mean particle size (nm), and ε: grade of the dispersion. **) It wasimpossible to measure the refractive indexes of Comparison Examples 1, 3and 4.

EXAMPLE 9 Preparation of Coating Liquid for High Refractive Index Layer

To the titanium dioxide dispersion of Example 1, a mixture ofdipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate[DPHA, Nippon Kayaku Co., Ltd.], a photopolymerization initiator[Irgacure 907, Ciba-Geigy], a photosensitizer [Kayacure DETX, NipponKayaku Co., Ltd.], and methyl ethyl ketone were added. The amount ofeach component was adjusted so that the resultant high refractive indexlayer would have a refractive index of 1.75.

Formation of High Refractive Index Layer

On a polyethylene terephthalate film having 90 μm thickness, a hardcoating layer was provided. The coating liquid for high refractive indexlayer was applied on the hard coating layer with a bar coater, andirradiated with UV light to harden. Thus, a high refractive index layerhaving 60 nm thickness (under dry condition) was formed.

Formation of Low Refractive Index Layer

6 g of dipentaerythritol hexaacrylate, 0.5 g of a photopolymerizationinitiator [Irgacure 907, Ciba-Geigy], 0.2 g of a photosensitizer[Kayacure DETX, Nippon Kayaku Co., Ltd.], and 20 g of ethyl acetate weredispersed and emulsified in 100 g of water with 1 g of sodiumdodecybenzenesulfonate. The emulsified liquid and 100 g of fineparticles (mean particle size: 52 nm) of copolymer of methylmethacrylate (80 weight parts)-divinylbenzene (25 weight parts) weremixed and stirred to form a coating liquid for low refractive indexlayer.

The coating liquid was applied on the high refractive index layer with abar coater to form a layer having a thickness of 100 nm. After drying,the layer was heated to 100° C., and irradiated with UV light of a 12W/cm high pressure mercury lamp for 1 minute to crosslink the polymer.The layer was cooled to room temperature, so as to form a low refractiveindex layer (refractive index: 1.55).

Thus, an anti-reflection film was produced.

The average reflectance (in the wavelength region of 400 to 700 nm) ofthe film was measured with a reflectance meter (V-550 and ARV-474,Nippon Bunko Co., Ltd.), and the haze of the film was also measured bymeans of a haze meter (NDH-1001DP, Nippon Denshoku Kogyo Co., Ltd.).Further, the mechanical strength was evaluated in terms of pencilhardness under a load of 1 kgw. The results are set forth in Table 2.

COMPARISON EXAMPLE 5

On the hard coating layer of Example 9, a mixture of dipentaerythritolpentaacrylate and dipentaerythritol hexaacrylate [DPHA, Nippon KayakuCo., Ltd.] was evenly applied, and irradiated with UV light to form alayer (refractive index: 1.53) having 60 nm thickness (under drycondition).

On thus formed layer, a low refractive index layer is formed in themanner of Example 9 to produce an anti-reflection film. The film wasevaluated. The results are set forth in Table 2.

COMPARISON EXAMPLE 6

Into the titanium dioxide dispersion of Comparison Example 2, a mixtureof dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate[DPHA, Nippon Kayaku Co., Ltd.], a photopolymerization initiator[Irgacure 907, Ciba-Geigy], a photosensitizer [Kayacure DETX, NipponKayaku Co., Ltd.], and methyl ethyl ketone were added. The amount ofeach component was adjusted so that the resultant high refractive indexlayer would have a refractive index of 1.75.

Except for using thus prepared coating liquid for high refractive indexlayer, the procedure of Example 9 was repeated to produce ananti-reflection film and to evaluate the film. The results are set forthin Table 2.

EXAMPLE 10

The procedure of Example 9 was repeated to prepare a high refractiveindex layer.

On thus formed layer, a low refractive index layer (refractive index:1.40) having 100 nm thickness of a silicon compound comprising finevoids was provided. The volume ratio of the fine voids was 6 vol. %.

The obtained anti-reflection film was evaluated in the manner of Example9. The results are set forth in Table 2.

EXAMPLE 11

The procedure of Example 9 was repeated to prepare a high refractiveindex layer.

On the layer, a coating liquid for low refractive index layer is appliedand dried to form a low refractive index layer having the thickness of100 nm (refractive index: 1.40). The coating liquid contained fineparticles and dipentaerythritol hexaacrylate as a binder (weight ratioof particles/binder: 84/16). The fine particles had the weight meanparticle size of 30 nm, and were made of copolymer ofhexafluoroisopropyl methacrylate (75 weight parts), 1,4-divinylbenzene(20 weight parts), 2-hydroxyethyl methacrylate (3 weight parts), andmethacrylic acid (2 weight parts). The formed low refractive index layerhad fine voids of 11 vol. % in terms of void volume.

The obtained anti-reflection film was evaluated in the manner of Example9. The results are set forth in Table 2.

TABLE 2 polymer in high re- fractive index layer α* β* haze γ* δ* Ex.9anionic crosslinked 65 1.55 0.3% 3H 2.3% CE.5 crosslinked —** 1.55 0.2%3H 5.2% CE.6 crosslinked/surface active agent 67 1.55 0.3% B 2.3% Ex.10anionic crosslinked 65 1.40 0.1% 3H 0.8% Ex.11 anionic crosslinked 651.40 0.1% 3H 0.8% Remarks: *) each of α, β, γ and δ is as follows. α:mean particle size (nm), β: refractive index of the low refractive indexlayer, γ: mechanical strength, and δ: reflectance. **) The highrefractive index layer of Comparison Example 5 does not contain fineparticles.

EXAMPLE 12 Preparation of Coating Liquid for Middle Refractive IndexLayer

To the titanium dioxide dispersion of Example 1, a mixture ofdipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate[DPHA, Nippon Kayaku Co., Ltd.], a photopolymerization initiator[Irgacure 907, Ciba-Geigy], a photosensitizer [Kayacure DETX, NipponKayaku Co., Ltd.], and methyl ethyl ketone were added. The amount ofeach component was adjusted so that the resultant middle refractiveindex layer would have a refractive index of 1.72.

Formation of Middle Refractive Index Layer

On a triacetylcellulose film having 90 μm thickness, a hard coatinglayer was provided. The coating liquid for middle refractive index layerwas applied on the hard coating layer with a bar coater, and irradiatedwith UV light to harden. Thus, a middle refractive index layer having 75nm thickness (under dry condition) was formed.

Preparation of Coating Liquid for High Refractive Index Layer

To the titanium dioxide dispersion of Example 1, a mixture ofdipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate[DPHA, Nippon Kayaku Co., Ltd.], a photopolymerization initiator[Irgacure 907, Ciba-Geigy], a photosensitizer [Kayacure DETX, NipponKayaku Co., Ltd.], and methyl ethyl ketone were added. The amount ofeach component was adjusted so that the resultant high refractive indexlayer would have a refractive index of 2.20.

Formation of High Refractive Index Layer

The coating liquid for high refractive index layer was applied on themiddle refractive index layer with a bar coater, and irradiated with UVlight to harden. Thus, a high refractive index layer having 80 nmthickness (under dry condition) was formed.

Formation of Low Refractive Index Layer

The procedure of Example 9 was repeated to prepare a low refractiveindex layer having 80 nm thickness on the high refractive index layer.Thus, an anti-reflection film was produced.

The average reflectance, the haze, and the mechanical strength of theproduced film were evaluated in the manner of Example 9. The results areset forth in Table 3.

COMPARISON EXAMPLE 7 Preparation of Coating Liquid for Middle RefractiveIndex Layer

To the titanium dioxide dispersion of Comparison Example 2, a mixture ofdipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate[DPHA, Nippon Kayaku Co., Ltd.], a photopolymerization initiator[Irgacure 907, Ciba-Geigy], a photosensitizer [Kayacure DETX, NipponKayaku Co., Ltd.], and methyl ethyl ketone were added. The amount ofeach component was adjusted so that the resultant middle refractiveindex layer would have a refractive index of 1.72.

Formation of Middle Refractive Index Layer

On a triacetylcellulose film having 90 μm thickness, a hard coatinglayer was provided. The coating liquid for middle refractive index layerwas applied on the hard coating layer with a bar coater, and irradiatedwith UV light to harden. Thus, a middle refractive index layer having 75nm thickness (after dryness) was formed.

Preparation of Coating Liquid for High Refractive Index Layer

To the titanium dioxide dispersion of Comparison Example 2, a mixture ofdipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate[DPHA, Nippon Kayaku Co., Ltd.], a photopolymerization initiator[Irgacure 907, Ciba-Geigy], a photosensitizer [Kayacure DETX, NipponKayaku Co., Ltd.], and methyl ethyl ketone were added. The amount ofeach component was adjusted so that the resultant high refractive indexlayer would have a refractive index of 2.20.

Formation of High Refractive Index Layer

The coating liquid for high refractive index layer was applied on themiddle refractive index layer with a bar coater, and irradiated with UVlight to harden. Thus, a high refractive index layer having 115 nmthickness (after dryness) was formed.

Formation of Low Refractive Index Layer

The procedure of Example 9 was repeated to prepare a low refractiveindex layer having 80 nm thickness on the high refractive index layer.Thus, an anti-reflection film was produced.

The average reflectance, the haze, and the mechanical strength of theproduced film were evaluated in the manner of Example 9. The results areset forth in Table 3.

EXAMPLE 13 Preparation of Coating Liquid for Middle Refractive IndexLayer

To the tin oxide dispersion of Example 3, a mixture of dipentaerythritolpentaacrylate and dipentaerythritol hexaacrylate [DPHA, Nippon KayakuCo., Ltd.], a photopolymerization initiator [Irgacure 907, Ciba-Geigy],a photosensitizer [Kayacure DETX, Nippon Kayaku Co., Ltd.], and methylethyl ketone were added. The amount of each component was adjusted sothat the resultant middle refractive index layer would have a refractiveindex of 1.72.

Formation of Middle Refractive Index Layer

On a triacetylcellulose film having 90 μthickness, a hard coating layerwas provided. The coating liquid for middle refractive index layer wasapplied on the hard coating layer with a bar coater, and irradiated withUV light to harden. Thus, a middle refractive index layer having 75 nmthickness (under dry condition) was formed.

Preparation of Coating Liquid for High Refractive Index Layer

To the titanium dioxide dispersion of Example 8, a mixture ofdipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate[DPHA, Nippon Kayaku Co., Ltd.], a photopolymerization initiator[Irgacure 907, Ciba-Geigy], a photosensitizer [Kayacure DETX, NipponKayaku Co., Ltd.], and methyl ethyl ketone were added. The amount ofeach component was adjusted so that the resultant high refractive indexlayer would have a refractive index of 2.20.

Formation of High Refractive Index Layer

The coating liquid for high refractive index layer was applied on themiddle refractive index layer with a bar coater, and irradiated with UVlight to harden. Thus, a high refractive index layer having 115 nmthickness (under dry condition) was formed.

Formation of Low Refractive Index Layer

The procedure of Example 10 was repeated to form a low refractive indexlayer (refractive index: 1.40) having 80 nm thickness on the highrefractive index layer. The formed layer had fine voids of 6 vol. % interms of void volume.

Thus, an anti-reflection film was produced.

The average reflectance, the haze, and the mechanical strength of theproduced film were evaluated in the manner of Example 9. The results areset forth in Table 3.

EXAMPLE 14

The procedure of Example 13 was repeated to form a middle refractiveindex layer and a high refractive index layer.

The procedure of Example 11 was repeated to prepare a low refractiveindex layer (refractive index: 1.40) having 80 nm thickness on the highrefractive index layer. The prepare layer had fine voids of 11 vol. % interms of void volume.

Thus, an anti-reflection film was produced.

The average reflectance, the haze, and the mechanical strength of theproduced film were evaluated in the manner of Example 9. The results areset forth in Table 3.

EXAMPLE 15 Preparation of Coating Liquid for Middle Refractive IndexLayer

Into the titanium dioxide dispersion of Example 8, a mixture ofdipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate[DPHA, Nippon Kayaku Co., Ltd.], a photopolymerization initiator[Irgacure 907, Ciba-Geigy], a photosensitizer [Kayacure DETX, NipponKayaku Co., Ltd.], and methyl ethyl ketone were added. The amount ofeach component was adjusted so that the resultant middle refractiveindex layer would have a refractive index of 1.72.

Formation of Middle Refractive Index Layer

On a triacetylcellulose film having 90 μm thickness, a hard coatinglayer was provided. The coating liquid for middle refractive index layerwas applied on the hard coating layer with a bar coater, and irradiatedwith UV light to harden. Thus, a middle refractive index layer having 75nm thickness (under dry condition) was formed.

Preparation of Coating Liquid for High Refractive Index Layer

To the titanium dioxide dispersion of Example 8, a mixture ofdipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate[DPHA, Nippon Kayaku Co., Ltd.], a photopolymerization initiator[Irgacure 907, Ciba-Geigy], a photosensitizer [Kayacure DETX, NipponKayaku Co., Ltd.], and methyl ethyl ketone were added. The amount ofeach component was adjusted so that the resultant high refractive indexlayer would have a refractive index of 2.20.

Formation of High Refractive Index Layer

The coating liquid for high refractive index layer was applied on themiddle refractive index layer with a bar coater, and irradiated with UVlight to harden. Thus, a high refractive index layer having 115 nmthickness (under dry condition) was formed.

Formation of Low Refractive Index Layer

The procedure of Example 11 was repeated to form a low refractive indexlayer (refractive index: 1.40) having 80 nm thickness on the highrefractive index layer. The formed layer had fine voids of 11 vol. % interms of void volume.

Thus, an anti-reflection film was produced.

The average reflectance, the haze, and the mechanical strength of theproduced film were evaluated in the manner of Example 9. The results areset forth in Table 3.

TABLE 3 polymer in high re- fractive index layer α* β* haze γ* δ* Ex.12anionic crosslinked 65 1.55 0.5% 3H 1.1% CE.7 crosslinked/surface activeagent 67 1.55 0.5% B 0.4% Ex.13 anionic crosslinked 65 1.40 0.5% 3H 0.3%Ex.14 anionic crosslinked 65 1.40 0.5% 3H 0.3% Ex.15 anionic crosslinked65 1.40 0.5% 3H 0.3% Remarks: *) each of α, β, γ and δ is as follows. α:mean particle size (nm), β: refractive index of the low refractive indexlayer, γ: mechanical strength, and δ: reflectance.

SYNTHESIS EXAMPLE 1 Surface Treatment of Inorganic Fine Particles

In a three neck flask of 500 ml having a reflux condenser, a thermometerand a stirrer, 300 ml of distilled water and 0.57 g of 70 wt. % aqueousdioctyl sodium sulfosuccinate (surface active agent) solution wereplaced and stirred to prepare a mixture. To the mixture, 90.0 g of 21.1wt. % colloidal dispersion of magnesium fluoride (particle size: 30.5nm) was slowly added. The pH of the liquid was adjusted to 7.5 using 2Nsulfuric acid. After heating to 80° C. under nitrogen gas atmosphere,1.0 g of 3-methacryloyloxypopyltrimethoxysilane was added and stirredfor 4 hours. Thus, the magnesium fluoride particles were subjected tosurface treatment.

Formation of Polymer Shell

To the surface treated magnesium fluoride particles, an aqueous solution(polymerization initiator solution) prepared by dissolving 0.128 g ofpotassium persulfate in 8 ml of distilled water was added. Immediately,4.5 g of hexafluoroisopropyl methacrylate (monomer) was dropwise addedfor 3 hours, and then the polymerization initiator solution was againadded. The reaction mixture was stirred at 80° C. for 3 hours tocomplete polymerization.

The liquid was cooled to room temperature, and filtered to prepare 415 gof core-shell fine particle dispersion (yield: 98%) having a solidcontent of 6.0 wt. % and a mean particle size of 40.2 nm.

SYNTHESIS EXAMPLE 2 Surface Treatment of Inorganic Fine Particles

In a four neck flask of 300 ml having a reflux condenser, a thermometerand a stirrer, 5 g of sodium dodecylsulfate, 300 g of colloidal silica[ST-ZL, Nissan Kagaku Co., Ltd.; mean particle size: 72 nm, solidcontent: 30 wt. %], and 74 ml of ion exchanged water were placed. The pHof the mixture was adjusted to 7.5 with 2N sulfuric acid, and stirred.After heating to 60° C. under nitrogen gas atmosphere, 10 g of3-methacryloyloxypopyltrimethoxysilane was added and stirred for 4hours. Thus, the silica particles were subjected to surface treatment.

Formation of Polymer Shell

To the surface treated silica particles, 0.5 g of potassium persulfateand 0.2 g of sodium bisulfite were added. Further, a mixture of 54 g ofhexafluoroisopropyl methacrylate, 4.8 g of glycidyl methacrylate, and1.2 g of acrylic acid was dropwise added for 3 hours while the reactiontemperature was kept at 60-70° C. Even after the addition was complete,the liquid was stirred for 2 hours while the temperature was still keptin the same level. The reaction mixture was cooled to room temperature,dialyzed for 3 days with a dialyzer having the fractional molecularweight of 10,000, and filtered to give 757 g of core-shell fine particledispersion (yield: 96%) having the solid content of 20.3 wt. % and themean particle size of 81.3 nm.

SYNTHESIS EXAMPLES 3-7

By the emulsion polymerization process similar to Synthesis examples 1and 2, shells of the following polymers were formed around the particlesto synthesize the core-shell fine particles set forth Table 4.

Synthesis Example 1: polyhexafluoroisopropyl methacrylate,

Synthesis Example 2: copolymer of hexafluoroisopropyl methacrylate (90weight parts)/glycidyl methacrylate (8 weight parts)/acrylic acid (2weight parts),

Synthesis Example 3: copolymer of hexafluoroisopropyl methacrylate (90weight parts)/glycidyl methacrylate (10 weight parts),

Synthesis Example 4: copolymer of 1H, 1H-pentadecafluorooctyl acrylate(95 weight parts)/2-hydroxyethyl methacrylate (5 weight parts),

Synthesis Example 5: copolymer of hexafluoroisopropyl α-fluoroacrylate(90 weight parts)/2-hydroxyethyl acrylate (10 weight parts),

Synthesis Example 6: copolymer of trifluoroethyl acrylate (80 weightparts)/glycidyl methacrylate (20 weight parts), and

Synthesis Example 7: copolymer of hexafluoroisopropyl methacrylate (90weight parts)/allyl methacrylate (10 weight parts).

TABLE 4 α* β* γ* δ* ε* ζ* Syn.Ex.1 MgF₂ 30.5 81/19 6.0 40.2 59.2Syn.Ex.2 SiO₂ 72.0 60/40 20.3 81.3 18.6 Syn.Ex.3 MgF₂ 30.5 70/30 8.253.9 56.7 Syn.Ex.4 SiO₂ 72.0 50/50 12.6 92.0 29.8 Syn.Ex.5 CaF₂ 55.490/10 11.3 61.4 48.8 Syn.Ex.6 CaF₂ 55.4 82/18 6.2 67.9 45.2 Syn.Ex.7MgF₂ 123.0 76/24 3.9 139.0 58.8 Remarks: *) each of α, β, γ, δ, ε and ζis as follows. α: core compound, β: core particle size (nm), γ: weightratio of core/shell, δ: solid content (wt. %), ε: mean particle size(nm), and ζ: content of fluorine (wt. %).

EXAMPLE 16

90 weight parts of the fine particles prepared in Synthesis Example 1and 10 weight parts of polymethyl methacrylate latex were mixed toprepare a coating dispersion for low refractive index layer.

The liquid was applied on a triacetylcellulose film with a spin coater,and dried at 90° C. for 90 minutes to form a low refractive index layerhaving 100 nm thickness. Thus, an anti-reflection film was produced.

The refractive index, the void ratio, the visible reflectance (averagereflectance in the wavelength region of 400 to 800 nm), and the surfacemechanical strength of the produced film were measured.

The refractive index of the layer was measured, and independently thetheoretical one was calculated in consideration of the components of thelayer. From the difference between the measured refractive index and thetheoretical value, the void ratio was evaluated. On the other hand, thefilm was rubbed with a finger, tissue paper or a rubber eraser, andobserved by sight to evaluate the surface mechanical strength. Accordingto the observation, the grade of the surface mechanical strength wasdetermined. The grade “A” means that the film was not damaged with anyof the above, and tha those of “B”, “C” and “D” mean that the film wasdamaged with a rubber eraser, tissue paper and a finger, respectively.The results are set forth in Table 5.

EXAMPLES 17-25 AND SYNTHESIS EXAMPLES 8-11

The procedure of Example 1 was repeated except that the compositions offine particles and polymer binders were changed as shown in Table 5, toproduce anti-reflection films. The films were evaluated in the manner ofExample 16, and the results are set forth in Table 5.

TABLE 5 particles binder ε* ζ* η* θ* α* β* γ* δ* Ex.16 Syn.Ex.1 90 BP3**10 1.33 0.5 A 18% Ex.17 Syn.Ex.1 85 BP1** 15 1.32 0.3 A 14% Ex.18Syn.Ex.3 100  — 0 1.31 0.3 A 21% Ex.19 Syn.Ex.3 90 BP1** 10 1.31 0.3 A17% Ex.20 Syn.Ex.3 80 BP3** 20 1.32 0.5 A 11% Ex.21 Syn.Ex.2 75 BP2** 251.34 0.6 A 7% Ex.22 Syn.Ex.4 75 BP2** 25 1.33 0.4 A 5% Ex.23 Syn.Ex.5 75BP2** 25 1.32 0.2 A 12% Ex.24 Syn.Ex.6 75 BP2** 25 1.33 0.4 A 9% Ex.25Syn.Ex.7 75 BP2** 25 1.31 0.3 A 9% CE.8 NP-1*** 75 BP1** 25 1.45 3.2 C1% CE.9 NP-2*** 80 BP2** 20 1.36 0.7 C 10% CE. NP-2*** 75 BP1** 25 1.340.5 B 9% 10 CE. None — BP1** 100 1.38 2.4 D 0% 11 Remarks: *) each of α,β, γ, δ, ε, ζ, η and θ is as follows. α: refractive index of the lowrefractive index layer, β: surface reflectance, γ: grade of mechanicalstrength, δ: void ratio, ε: material of particles, ζ: content ofparticles (wt. %), η: material of binders, and θ: content of binders(wt. %). **) each of BP1, BP2 and BP3 is as follows. BP1:polyhexafluoroisopropyl methacrylate latex, BP2: copolymer latex ofhexafluoroisopropyl methacrylate (9 weight parts) /divinylbenzene (9weight parts), and BP3: polymethyl methacrylate latex. ***) each of NP-1and NP-2 is as follows. NP-1: fine particles (mean particle size: 52 nm)of copolymer of methyl methacrylate (80 weight parts)/divinyl benzene(25 weight parts), and NP-2: fine particles (mean particle size: 61 nm)consisting of copolymer core (70 wt. %) of hexafluoroisopropylmethacrylate (80 weight parts)/divinyl benzene(20 weights parts) andcopolymer shell (30 wt. %) of hexafluoroisopropyl methacrylate (90weight parts)/glycidyl methacrylate (10 weight parts).

EXAMPLE 26 Formation of Hard Coating Layer

Dipentaerythritol hexaacrylate, a photopolymerization initiator[Irgacure 907, Ciba-Geigy], and a photosensitizer [Kayacure DETX, NipponKayaku Co., Ltd.] were dissolved in toluene in amounts of 5 wt. %, 0.5wt. % and 0.2 wt. %, respectively. The prepared solution was applied ona triacetylcellulose film having 90 μm thickness by means of a wire bar,and dried to form a layer having a thickness of 8 μm. The formed layerwas heated to 100° C., and irradiated with UV light of a 12 W/cm highpressure mercury lamp for 1 minute to crosslink the polymer. The layerwas then cooled to room temperature.

Formation of High Refractive Index Layer

100 g of copolymer latex (mean particles size: 71 nm, solid content:12.5 wt. %) of n-butyl methacrylate (80 weight parts)/methacrylic acid(20 weight parts) and 25 g tin oxide particles (available from IshiharaSangyo Co., Ltd.) were mixed. Independently, 6 g of dipentaerythritolhexaacrylate, 0.5 g of a photopolymerization initiator [Irgacure 907,Ciba-Geigy], 0.2 g of a photosensitizer [Kayacure DETX, Nippon KayakuCo., Ltd.], and 20 g of ethyl acetate were dispersed and emulsified in100 g of water containing 1 g of sodium dodecybenzenesulfonate. Thusprepared latex and the emulsified liquid were mixed to prepare a coatingliquid for high refractive index layer. The prepared liquid was appliedon the hard coating layer by means of a wire bar, to form a highrefractive index layer having the thickness of 0.16 μm. After drying,the formed layer was heated to 100° C., and irradiated with UV light ofa 12 W/cm high pressure mercury lamp for 1 minute to crosslink thepolymer. The layer was then cooled to room temperature.

Formation of Low Refractive Index Layer

6 g of dipentaerythritol hexaacrylate, 0.5 g of a photopolymerizationinitiator [Irgacure 907, Ciba-Geigy], 0.2 g of a photosensitizer[Kayacure DETX, Nippon Kayaku Co., Ltd.], and 20 g of ethyl acetate weredispersed and emulsified in 100 g of water with 1 g of sodiumdodecybenzenesulfonate. The emulsified liquid and 100 g of the fineparticles prepared in Synthesis Example 1 were mixed and stirred toprepare a coating liquid for low refractive index layer.

The prepared liquid was applied on the hard refractive index layer bymeans of a wire bar, to form a low refractive index layer having thethickness of 0.10 μm. After drying, the formed layer was heated to 100°C., and irradiated with UV light of a 12 W/cm high pressure mercury lampfor 1 minute to crosslink the polymer. The layer was then cooled to roomtemperature.

Thus, an anti-reflection film was produced.

The visible reflectance and the surface mechanical strength of theproduced film were evaluated in the manner of Example 16, and found 0.3%and grade “A”, respectively.

EXAMPLES 27-31 AND COMPARISON EXAMPLES 12 AND 13

The procedure of Example 26 was repeated except that the polymer in thehigh refractive index layer and the fine particles in low refractiveindex were changed as shown in Table 6, to produce anti-reflectionfilms. The concentration of each coating liquid was adjusted so that theliquid might have the same solid content as that in Example 26. Thevisible reflectance and the surface mechanical strength of each producedfilm were evaluated, and the results are set forth in Table 6.

TABLE 6 high r. layer low r. layer surface strength polymer r.index fineparticles reflect. grade Ex.26 HP1* 1.55 Syn.Ex.1 0.3% A Ex.27 HP2* 1.57Syn.Ex.3 0.3% A Ex.28 HP3* 1.59 Syn.Ex.3 0.2% A Ex.29 HP2* 1.57 Syn.Ex.40.4% A Ex.30 HP1* 1.55 Syn.Ex.5 0.2% A Ex.31 HP3* 1.59 Syn.Ex.7 0.3% ACE.12 HP1* 1.55 NP-1** 4.2% C CE.13 HP1* 1.55 NP-2** 0.3% C Remarks: *)each of HP1, HP2 and HP3 is as follows. HP1: copolymer of n-butylmethacrylate (80 weight parts)/methacrylic acid (20 weight parts), HP2:copolymer of methyl methacrylate (65 weight parts)/ethyl methacrylate(25 weight parts)/glycidyl methacrylate (10 weight parts), and HP3:copolymer of benzyl methacrylate (50 weight parts)/methyl methacrylate(25 weight parts)/allyl methacrylate (20 weight parts)/methacrylic acid(5 weight parts). **) each of NP-1 and NP-2 is as follows. NP-1: fineparticles (mean particle size: 52 nm) of copolymer of methylmethacrylate (80 weight parts)/divinyl benzene (25 weight parts), andNP-2: fine particles (mean particle size: 61 nm) consisting of copolymercore (70 wt. %) of hexafluoroisopropyl methacrylate (80 weightparts)/divinyl benzene (20 weights parts) and copolymer shell (30 wt. %)of hexafluoroisopropyl methacrylate (90 weight parts)/glycidylmethacrylate (10 weight parts).

EXAMPLE 32

The anti-reflection film prepared in Example 27 was fixed on the liquidcrystal display screen of personal computer (PC9821NS/340W, NipponElectric Co., Ltd.). The image displayed on the screen equipped with thefilm was observed to confirm that surrounding scene was scarcelyreflected in the screen, and that the film gave excellent viewability.

EXAMPLE 33

The anti-reflection film prepared in Example 28 was fixed on the liquidcrystal display screen of personal computer (PC9821NS/340W, NipponElectric Co., Ltd.). The image displayed on the screen equipped with thefilm was observed to confirm that surrounding scene was scarcelyreflected in the screen, and that the film gave excellent viewability.

EXAMPLE 34

The anti-reflection film prepared in Example 30 was fixed on the liquidcrystal display screen of personal computer (PC9821NS/340W, NipponElectric Co., Ltd.). The image displayed on the screen equipped with thefilm was observed to confirm that surrounding scene was scarcelyreflected in the screen, and that the film gave excellent viewability.

COMPARISON EXAMPLE 14

The anti-reflection film prepared in Comparison Example 12 was fixed onthe liquid crystal display screen of personal computer (PC9821NS/340W,Nippon Electric Co., Ltd.). The image displayed on the screen equippedwith the film was observed to confirm that surrounding scene wasconsiderably reflected in the screen, and that the film gave poorviewability as compared with those of the films of Examples 32 to 34.

COMPARISON EXAMPLE 15

The anti-reflection film prepared in Comparison Example 13 was fixed onthe liquid crystal display screen of personal computer (PC9821NS/340W,Nippon Electric Co., Ltd.). The image displayed on the screen equippedwith the film was observed to confirm that surrounding scene wasconsiderably reflected in the screen, and that the film gave poorviewability as compared with those of the films of Examples 32 to 34.

EXAMPLE 35 Formation of Hard Coating Layer

125 g of a mixture of dipentaerythritol pentaacrylate anddipentaerythritol hexaacrylate [DPHA, Nippon Kayaku Co., Ltd.] and 125 gof urethane acrylate oligomer [UV-6300B, Nippon Goseikagaku Kogyo Co.,Ltd.] were dissolved in 439 g of industrial denatured ethanol. To theobtained solution, a solution prepared by dissolving 7.5 g of aphotopolymerization initiator [Irgacure 907, Ciba-Geigy] and 5.0 g of aphotosensitizer [Kayacure DETX, Nippon Kayaku Co., Ltd.] in 49 g ofmethyl ethyl ketone was added. After stirring, the mixture was filteredthrough 1 μm mesh to prepare a coating liquid for hard coating layer.

On a triacetylcellulose film [TAC-TD80U, Fuji Photo Film Co., Ltd.]having 80 μm thickness, a gelatin undercoating layer was provided. Thecoating liquid for hard coating layer was applied on the undercoatinglayer with a bar coater, dried at 120° C., and irradiated with UV lightto harden. Thus, a hard coating layer having 7.5 μm thickness wasformed.

Preparation of Coating Liquid for Low Refractive Index Layer

200 g of methanol dispersion of fine silica particles [R507, NissanKagaku Co., Ltd.], 10 g of silane coupling agent [KBN-803, Shin-EtsuSilicon Co., Ltd.] and 2 g of 0.1 N hydrochloric acid were mixed andstirred at room temperature for 5 hours, and then stored at roomtemperature for about 6 days. Thus, a dispersion of fine silicaparticles subjected to silane treatment was prepared.

To 149 g of the dispersion, 789 g of isopropyl alcohol and 450 g ofmethanol were added. To the obtained mixture, a solution prepared bydissolving 3.21 g of a photopolymerization initiator [Irgacure 907,Ciba-Geigy] and 1.605 g of a photosensitizer [Kayacure DETX, NipponKayaku Co., Ltd.] in 31.62 g of isopropyl alcohol was added. Further, asolution prepared by dissolving 2.17 g of a mixture of dipentaerythritolpentaacrylate and dipentaerythritol hexaacrylate [DPHA, Nippon KayakuCo., Ltd.] in 78.13 g of isopropyl alcohol was added. The thus preparedmixture was stirred at room temperature for 20 minutes, and filteredthrough 1 μm mesh to prepare a coating liquid for low refractive indexlayer.

Production of Anti-reflection Film

The coating liquid for low refractive index layer was applied on thehard coating layer with a bar coater, dried at 120° C., and irradiatedwith UV light to form a low refractive index layer (thickness: 0.1 μm).Thus, an anti-reflection film was produced.

The average reflectance in the wavelength region of 450 to 650 nm of thefilm was measured, and the surface mechanical strength was evaluated interms of pencil hardness. The results are set forth in Table 7.

EXAMPLE 36

On a polyethylene terephthalate film having 100 μm thickness, a gelatinundercoating layer was provided. The coating liquid for hard coatinglayer of Example 35 was applied on the undercoating layer with a barcoater, dried at 120° C., and irradiated with UV light to harden. Thus,a hard coating layer having 7.5 μm thickness was formed.

The procedure of Example 21 was repeated to form a low refractive indexlayer on the hard coating layer, to produce an anti-reflection film.

The average reflectance in the wavelength region of 450 to 650 nm of thefilm was measured, and the surface mechanical strength was evaluated interms of pencil hardness. The results are set forth in Table 7.

EXAMPLE 37

The surface of a syndiotactic polystyrene film having 100 μm thicknesswas subjected to glow discharge treatment. The coating liquid for hardcoating layer of Example 35 was applied on the thus treated film with abar coater, dried at 120° C., and irradiated with UV light to harden.Thus, a hard coating layer having 7.5 μm thickness was formed.

The procedure of Example 35 was repeated to form a low refractive indexlayer on the hard coating layer, to produce an anti-reflection film.

The average reflectance in the wavelength region of 450 to 650 nm of thefilm was measured, and the surface mechanical strength was evaluated interms of pencil hardness. The results are set forth in Table 7.

TABLE 7 transparent support void strength material re.index ratioreflect. grade Ex.35 triacetylcellulose 1.48 14% 1.5% 2H Ex.36polyethylene tere- 1.66 14% 1.3% 2H phthalate Ex.37 polystyrene 1.58 14%1.4% 2H

EXAMPLE 38 Preparation of Titanium Dioxide Dispersion

30 weight parts of titanium dioxide [weight mean particle size ofprimary particles: 50 nm, refractive index: 2.70], 3 weight parts of theanionic monomer (1) in Example 1, 3 weight parts of the anionic monomer(2) in Example 1, 1 weight part of the cationic monomer in Example 8,and 63 weight parts of methyl ethyl ketone were mixed by means of a sandgrinder to prepare a dispersion of titanium dioxide.

Preparation of Coating Liquid for Middle Refractive Index Layer

0.18 g of a photopolymerization initiator [Irgacure 907, Ciba-Geigy] and0.059 g of a photosensitizer [Kayacure DETX, Nippon Kayaku Co., Ltd.]were dissolved in 172 g of cyclohexanone and 43 g of methyl ethylketone. To the obtained solution, a mixture of 15.8 g of the titaniumdioxide dispersion and 3.1 g of a mixture of dipentaerythritolpentaacrylate and dipentaerythritol hexaacrylate [DPHA, Nippon KayakuCo., Ltd.] were added and stirred at room temperature for 30 minutes.The liquid was filtered through 1 μm mesh to prepare a coating liquidfor middle refractive index layer.

Preparation of Coating Liquid for High Refractive Index Layer

0.085 g of a photopolymerization initiator [Irgacure 907, Ciba-Geigy]and 0.028 g of a photosensitizer [Kayacure DETX, Nippon Kayaku Co.,Ltd.] were dissolved in 183 g of cyclohexanone and 46 g of methyl ethylketone. To the obtained solution, a mixture of 17.9 g of the titaniumdioxide dispersion and 1.0 g of a mixture of dipentaerythritolpentaacrylate and dipentaerythritol hexaacrylate [DPHA, Nippon KayakuCo., Ltd.] were added and stirred at room temperature for 30 minutes.The liquid was filtered through 1 μmesh to prepare a coating liquid forhigh refractive index layer.

Production of Anti-reflection Film

The coating liquid for middle refractive index layer was applied on thehard coating layer formed in Example 35 with a bar coater, dried at 120°C., and irradiated with UV light to form a middle refractive index layer(thickness: 0.081 μm).

The coating liquid for high refractive index layer was applied on themiddle refractive index layer with a bar coater, dried at 120° C., andirradiated with UV light to form a high refractive index layer(thickness: 0.053 μm).

The coating liquid for low refractive index layer of Example 35 wasapplied on the high refractive index layer with a bar coater, dried at120° C., and irradiated with UV light to form a low refractive indexlayer (thickness: 0.092 μm).

Thus, an anti-reflection film was produced.

The average reflectance in the wavelength region of 450 to 650 nm of thefilm was measured, and the surface mechanical strength was evaluated interms of pencil grades. Further, the contact angle of the surface wasalso measured to estimate whether the film is easily stained with fingerprints. The results are set forth in Table 8.

EXAMPLE 39

The procedure of Example 38 was repeated except that the thickness ofthe low refractive index layer was set at 0.072 μm, to provide middle,high and low refractive index layers on the hard coating layer. Asolution of crosslinkable polymer containing fluorine was applied on thelow refractive index layer, and heated at 120° C. to crosslink thepolymer. Thus, a protective layer having the thickness of 0.02 μm wasformed to produce an anti-reflection film.

The average reflectance in the wavelength region of 450 to 650 nm of thefilm was measured, and the surface mechanical strength was evaluated interms of pencil grades. Further, the contact angle of the surface wasalso measured to estimate whether the film is easily stained with fingerprints. The results are set forth in Table 8.

TABLE 8 strength contact protective layer reflect. grade angle Ex.38 notprovided 0.35% 2H 106° Ex.39 provided 0.36% 2H  28°

What is claimed is:
 1. An anti-reflection film comprising a highrefractive index layer having a refractive index of 1.65 to 2.40 and alow refractive index layer having a refractive index of 1.20 to 1.55,wherein the high refractive index layer contains inorganic fineparticles having a mean particle size of 1 to 200 nm in an amount of 5to 65 vol. % and a crosslinked polymer comprising a phosphoric acidgroup or a sulfonic acid group as an anionic group in an amount of 35 to95 vol. %.
 2. The anti-reflection film of claim 1, wherein the polymerhaving the anionic group in the high refractive index layer furthercomprises an amino group or an ammonium group.
 3. The anti-reflectionfilm of claim 1, wherein the inorganic fine particles in the highrefractive index layer have an average refractive index of 1.80 to 2.80.4. The anti-reflection film of claim 1, wherein the high refractiveindex layer is formed by applying a coating liquid, and the polymerhaving the anionic group is formed by polymerization reaction during orafter the application.
 5. The anti-reflection film of claim 1, whereinthe low refractive index layer contains inorganic fine particles havinga mean particle size of 0.5 to 200 nm in an amount of 50 to 95 wt. % anda polymer in an amount of 5 to 50 wt. %, and two or more of saidparticles are piled up to form micro voids among the particles.
 6. Theanti-reflection film of claim 5, wherein the void volume in the lowrefractive index layer is in the range of 3 to 50 vol. %.
 7. Theanti-reflection film of claim 5, wherein the inorganic fine particles inthe low refractive index layer are coated with a shell made of apolymer.
 8. The anti-reflection film of claim 5, wherein the micro voidsin the low refractive index layer are enclosed with the inorganicparticles and the polymer.
 9. A display device having, on its displayscreen, an anti-reflection film which comprises a high refractive indexlayer having a refractive index of 1.65 to 2.40 and a low refractiveindex layer having a refractive index of 1.20 to 1.55, wherein the highrefractive index layer contains inorganic fine particles having a meanparticle size of 1 to 200 nm in an amount of 5 to 65 vol. % and acrosslinked polymer comprising a phosphoric acid group or a sulfonicacid group as an anionic group in an amount of 35 to 95 vol. %.